Official Transcript of Proceedings NUCLEAR REGULATORY COMMISSION

Official Transcript of Proceedings
NUCLEAR REGULATORY COMMISSION
Title:
Advisory Committee on Nuclear Waste
135th Meeting
Docket Number:
(not applicable)
Location:
Rockville, Maryland
Date:
Wednesday, June 19, 2002
Work Order No.:
NRC-434
NEAL R. GROSS AND CO., INC.
Court Reporters and Transcribers
1323 Rhode Island Avenue, N.W.
Washington, D.C. 20005
(202) 234-4433
Pages 220-323
220
1
UNITED STATES OF AMERICA
2
NUCLEAR REGULATORY COMMISSION
3
+ + + + +
4
ADVISORY COMMITTEE ON NUCLEAR WASTE (ACNW)
5
135TH MEETING
6
+ + + + +
7
WEDNESDAY,
8
JUNE 19, 2002
9
+ + + + +
10
ROCKVILLE, MARYLAND
11
+ + + + +
12
The Advisory Committee met at 8:30 A.M. AT
13
the Nuclear Regulatory Commission, Two White Flint
14
North, Room T2B3, 11545 Rockville Pike, Dr. George M.
15
Hornberger, Chairman, presiding.
16
17
COMMITTEE MEMBERS PRESENT:
18
GEORGE M. HORNBERGER, Chairman
19
RAYMOND G. WYMER, Vice Chairman
20
B. JOHN GARRICK, Member
21
MILTON N. LEVENSON, Member
22
23
24
25
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1
ACNW STAFF PRESENT:
2
HOWARD J. LARSON, Special Assistant, ACRS/ACNW
3
SHER BAHADUR, Associate Director, ACRS/ACNW
4
ANDREW C. CAMPBELL
5
LYNN DEERING
6
TIMOTHY KOBETZ
7
MICHAEL LEE
8
RICHARD K. MAJOR
9
RICHARD P. SAVID
10
11
ALSO PRESENT:
12
TAE M. AHN
13
TAMARA BLOOMER
14
STEPHANIE P. BUSH-GODDARD
15
DAVID W. ESH
16
CAROL HANLON
17
BRET LESLIE
18
TIM McMARTIN
19
JACOB PHILIP
20
MERAJ RAHIMI
21
22
23
24
25
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1
I-N-D-E-X
2
Opening Statement . . . . . . . . . . . . . . .
3
Entombment Option for Decommissioning Power
4
Reactors
. . . . . . . . . . . . . . . .
223
224
5
Long-Term Behavior of Waste Packages
. . . . .
238
6
Adjourn . . . . . . . . . . . . . . . . . . . .
323
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
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1
P-R-O-C-E-E-D-I-N-G-S
2
8:30 A.M.
3
CHAIRMAN HORNBERGER:
The meeting will
4
come to order.
5
meeting of the Advisory Committee on Nuclear Waste.
6
My name is George Hornberger, Chairman of the ACNW.
7
The
8
Raymond Wymer, Vice Chairman; John Garrick and Milton
9
Levenson.
other
This is the second day of the 135th
Members
of
the
Committee
present
are:
10
Today, the Committee will (1) hear from
11
the NRC staff on comments received on the Rulemaking
12
Plan
13
Entombment Options for Power Reactors, although there
14
will be an amendment to that.
15
upon introduction. (2) Hearing presentations from the
16
NRC and CNWRA staff on issues and activities related
17
to the projected performance of waste packages in the
18
proposed
19
Mountain. (3) Discuss elements of a letter report on
20
the
21
Continue its discussion of other proposed reports.
and
Yucca
22
23
Notice
high-level
Mountain
of
waste
Review
Proposed
Rulemaking:
We'll hear about that
repository
Plan,
at
Yucca
Revision.
(4)
Howard J. Larson is the Designated Federal
Official for today's initial session.
24
25
Advanced
This
meeting
is
being
conducted
in
accordance with the provisions of the Federal Advisory
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1
Committee Act.
2
or requests for time to make oral statements from
3
members of the public regarding today's sessions.
4
Should anyone wish to address the Committee, please
5
make your wishes known to one of the Committee staff.
6
It
7
microphones,
8
sufficient clarity and volume so that they can be
9
readily heard.
is
We have received no written comments
requested
that
identify
speakers
themselves
use
and
one
of
speak
the
with
10
Okay, so as I had indicated just a moment
11
ago our first topic is going to be the entombment
12
option for decommissioning power reactors and the
13
cognizant member of the ACNW for this topic is Ray
14
Wymer, so I will turn the meeting over to Ray.
15
VICE CHAIRMAN WYMER:
of
entombment
of
Thank you.
decommissioning
The
16
business
power
17
reactors is one that is a subject of discussion and
18
concern to the ACNW for quite some time.
19
written a letter on it and we have a commit from the
20
staff to keep us updated and keep us current on the
21
status and I understand that what we're going to hear
22
this morning is just that.
23
report, where we stand and where we're going in the
24
future and Stephanie Goddard-Bush is going to tell us
25
all about that.
We've
It's a current status
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DR. BUSH-GODDARD:
Good morning.
2
VICE CHAIRMAN WYMER: Bush-Goddard, sorry.
3
(Laughter.)
4
DR. BUSH-GODDARD:
As Dr. Wymer said, my
5
name is Stephanie Bush-Goddard and I will be giving
6
you an update and next steps on entombment options for
7
decommissioning power reactors.
8
(Slide change.)
9
DR. BUSH-GODDARD:
I have five issues on
today.
over
10
the
agenda
I'll
go
NRC
papers
and
11
activities, a kind of background that led us into
12
rulemaking.
13
the Advanced Notice of Proposed Rulemaking issues.
14
Then I'll talk about some of the stakeholders' views
15
and comments from the Advanced Notice of Proposed
16
Rulemaking, and end with the staff recommendations.
I'll go over the rulemaking options and
17
(Slide change.)
18
DR. BUSH-GODDARD:
So I'll begin with NRC
19
papers and activities.
To refresh your memory, in
20
1997,
requested
21
determine the viability of an entombed facility.
22
a result, SECY 98-099 was developed.
23
Research provided the results of this study and the
24
results was that entombment was a viable process.
25
Also,
the
in
Commission
1999,
the
Office
of
that
the
staff
As
The Office of
Research
solicited
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1
stakeholders' views in a public workshop held here.
2
And from that SECY 00-0129 was Workshop Findings and
3
Recommendations.
4
of views and issues that were raised in the workshop
5
and a recommendation was that the staff should go into
6
rulemaking.
7
that paper was published or sent to the Commission in
8
June of last year. There was a rulemaking plan and an
9
Advanced Notice of Proposed Rulemaking.
10
In that paper, there was a summary
That resulted in the last SECY here and
The Advanced Notice of Proposed Rulemaking
11
was published for a 75-day comment period.
However,
12
in the rulemaking plan and the Advanced Notice of
13
Proposed Rulemaking, there were three options.
14
(Slide change.)
15
DR. BUSH-GODDARD: The first option was to
16
do nothing, to maintain the status quo, to keep the
17
60-year decommissioning time frame in place and handle
18
entombment on a case-by-case basis.
19
The
second
option
was
to
extend
the
20
decommissioning deadline beyond the 60 years and to
21
clarify the difference between engineered barriers and
22
institutional controls in terms of their effectiveness
23
in protecting the public.
24
And the third option was to create a new
25
license type, to provide for an entombed facility
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which would be a new type of disposal license.
2
(Slide change.)
3
DR. BUSH-GODDARD:
From the three options
4
we also had five different issues that were also
5
published in the ANPR and we requested stakeholder
6
input.
7
regulations were adequate and if not, what changes
8
were needed.
For example, we asked about whether the
9
10
We solicited about stakeholder views on
types and capabilities of engineered barriers.
11
We solicited input on how to dispose of
12
GTCC waste, whether we should remove it or entombment.
13
What were the views of the states and what
14
were their roles?
15
16
Lastly, if any licensee planed to entomb
their plant, when would they do it?
17
(Slide change.)
18
DR. BUSH-GODDARD: So from those issues we
19
received 19 comments and I have listed there we had 6
20
states, 8 licensees, NEI, EPA, CRCPD Committee.
21
had a compact and a private citizen.
22
We
Overall, there was no clear consensus.
23
There
were
many
caveats
suggested
for
all
three
24
options.
25
favored Option 1, but most licensees favored Option 2
Two commenters, New York State and Kansas
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with some caveats and Washington State was the only
2
commenter that advocated for Option 3.
3
(Slide change.)
4
DR. BUSH-GODDARD:
So from the working
5
group and management discussions, as well as looking
6
at the NPR, we decided to defer the rulemaking and the
7
reasoning behind that is that current regulations
8
don't explicitly permit entombment, but they don't
9
preclude it either.
on
a
So entombed facilities could be
10
addressed
case-by-case
basis.
Also,
if
11
decommissioning takes longer than 60 years, then the
12
GEIS may have to be revisited.
13
A third reasoning was that the roles of
14
the Department of Energy and the states were unclear
15
as they relate to GTCC.
16
noted that they have a regulatory role in this case
17
and that entombing greater than Class C wastes in a
18
reactor plant would adversely impact the low-level
19
regional waste compacts.
The states that commented
20
Another reason was that although some
21
licensees stated that they would like to have an
22
entombment,
23
imminent by any means.
24
that there's no immediate need to an entombed option,
25
we looked at NRC priorities.
as
an
option,
the
decision
was
not
And finally, given the fact
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As you may know, we are working on Yucca
2
Mountain and anticipate many more activities related
3
to physical security and the control of radioactive
4
materials.
5
6
Some of this will impact the regulatory
framework for an entombed facility.
7
(Slide change.)
8
DR. BUSH-GODDARD:
9
steps.
So finally, our next
Well, the staff is working on a SECY paper
10
transmitting our recommendation which is to defer
11
rulemaking
12
completed in October of this year.
13
Research
14
capabilities of concrete.
15
be completed in about three years.
16
interaction with the stakeholders on an entombment
17
option through conferences and forums and in the
18
meantime we continue to look at what we need to create
19
a performed-based regulatory framework.
to
is
the
Commission
currently
20
Thank you.
21
VICE
and
looking
CHAIRMAN
this
at
should
be
The Office of
the
structural
The study is scheduled to
There's continual
WYMER:
Thank
you,
22
Stephanie. That brings us up to date pretty well. It
23
seems just my offhand impression, this seems like a
24
sensible course since there's no current plan by
25
anybody that we know for entombment and most everybody
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is going other reactor operators and utilities are
2
going to the 20-year extension for the licensing
3
application and if anything does come up with respect
4
to entombment it will be an individual case that can
5
be handled on a case by case basis. Everything you've
6
said seems very reasonable to me.
7
8
Let
ask
for
comments
from
here.
don't
have
George?
9
10
me
CHAIRMAN
HORNBERGER:
I
anything.
11
VICE CHAIRMAN WYMER:
12
MEMBER GARRICK:
John?
The only thing I would
13
ask is was there anything particularly interesting
14
that came out of the public comments that had a heavy
15
influence on the actions you've taken?
16
DR. BUSH-GODDARD:
I think the biggest
17
thing was that there was no immediate need.
We did
18
have two questions in the ANPR that specifically said
19
how many licensees would like to do entombment, when
20
and when would they like to do it?
21
different caveats. They said, you know, we would like
22
-- we don't necessarily want to maybe do entombment,
23
but we want that option.
24
and you know, the availability of low level waste
25
sites.
There are a lot of
Or, it will depend on cost
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So the big issue, I think, that came out
2
of the comments was that there was no immediate need.
3
MEMBER GARRICK:
Is there much expression
4
of interest at this point from the licensees in this
5
approach in the entombment approach?
6
DR. BUSH-GODDARD:
Well, we had eight
7
licensees to comment and we also had the industry,
8
NEI.
9
them based on the number that commented.
I would say that it's not a high priority for
10
MEMBER GARRICK:
Okay, thank you.
11
VICE CHAIRMAN WYMER:
Milt, do you have
12
any questions or comments?
13
anybody around the table here want to -- Sher?
14
DR. BAHADUR:
in
the
rulemaking
How about the staff, does
Stephanie, you mentioned
15
that
options
there
were
three
16
options, either maintain the status quo, or amend the
17
50.82 or create a new license type.
18
Could you just tell us, maybe what were
19
the pros and cons of each one of these options were?
20
DR. BUSH-GODDARD: Yes. The first one was
21
to maintain the status quo.
A big pro was that the
22
status quo already permitted entombment.
23
years to decommission, but it is a regulation.
You have 60
24
A con is that if you need to go beyond the
25
60 years, you might have to apply for an exemption, so
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that means regulating by exemption.
2
As far as Option 2 which was to amend the
3
60-year time frame, a pro for that would be you would
4
not necessarily have to regulate by exemption, but a
5
disadvantage of that is that you might have to revisit
6
the GEIS.
7
course, because you're amending a regulation.
8
could be more resources to the licensee, depending on
9
how you look at than Option 1.
10
It's more resources than Option 1, of
It
Option 3 was to develop maybe a new part
11
or a new type of license.
The pro for that was that
12
it could possibly handle the disposal GTCC waste. The
13
Commission requested that we look at disposal of GTCC
14
waste in an entombed facility and the only way that we
15
could do that under the -- develop that was that the
16
facility had to be licensed because GTCC has to be in
17
some type of licensed facility.
18
a way of how we could dispose of GTCC, so that was the
19
big pro for that.
So Option 3 was more
20
However, the negative part of Option 3 was
21
that it required a lot of staff resources to develop
22
a new part.
23
than Option 1 and 2.
24
25
It was more expensive to the licensees
DR. BAHADUR:
So in the public comments,
of course, you had no clear consensus one way or the
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other, but I noticed that at least six people, six
2
comments favored Option 2.
3
DR. BUSH-GODDARD:
4
DR. BAHADUR:
Yes.
Is there a reason why --
5
although it's not a priority from our point of view,
6
also from the licensees, but did they mention any
7
reason why they were favoring Option 2?
8
9
DR. BUSH-GODDARD:
Yes.
The majority of
stakeholders that favored Option 2 were licensees and
10
NEI.
And Option 2 from their standpoint, they felt
11
they do unnecessary burden.
12
Option
13
flexibility than Option 1.
3,
14
but
it
gave
them
It was cheaper than
a
little
And
16
Department of Energy to take GTCC waste.
17
really want to have to deal with it.
18
DR. BAHADUR:
also,
come
to
think
of
it,
they
wanted
the
They didn't
But that's true even if you
go the status quo.
20
DR. BUSH-GODDARD:
21
DR. BAHADUR:
22
more
I guess those were the big two issues.
15
19
bit
Yes.
Greater than Class C would
be the DOE's responsibility.
23
DR. BUSH-GODDARD:
That's right, but I
24
guess the problem they had with Option 1 was that they
25
didn't feel that the majority of licensees could
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entomb within 60 years.
2
really extend that time frame which was Option 2.
3
MR. LEE:
That's why they wanted to
Stephanie, on Slide 5 or Slide
4
6, your ANP or comment summary, you noted that you had
5
19 sets of comments, but I counted 9.
6
under your second tick shows 9. What did the other 10
7
commenters have to say or if it's possible to kind of
8
give you a sense for what they --
9
DR. BUSH-GODDARD:
Your tally
Okay, the other 10 did
10
not come out with any preferred option.
For example,
11
the EPA, they basically said we don't have a preferred
12
option to make sure that you coordinate with DOE to
13
handle the GTCC.
14
going to entomb to consider chemical contaminants as
15
well as radioactive contaminants.
They asked us to look at if we were
16
The private citizen that commented wanted
17
to make sure that we keep active records and good
18
institutional controls, issues like that.
19
20
The CRCPD Committee just really summarized
a lot of the states' issues.
21
MR. LEE:
22
DR. BUSH-GODDARD:
23
MR. LEE:
made
earlier
Okay.
Things like that.
Keying back on an observation
24
you
that
the
low
volume
of
public
25
comments, regarding the low volume of comments, it
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might be possible that there was just an indifference
2
to the rulemaking proposal and that some organizations
3
or utilities aren't in the position to formulate an
4
opinion regarding the rulemaking proposal.
5
6
I mean that's another way to interpret the
volume, if you will, of the public response.
7
MR. LARSON:
Well, another thing is that
8
there are license extension and license renewals,
9
there have been a lot of them in the last few years
10
since before this thing started years ago. I guess my
11
question was I see they're going to do a research
12
program on concrete and I don't know if the Committee
13
has heard about it, whether what that involved.
14
15
MR.
audience.
16
17
LEE:
I
see
Jake
Philip
in
the
Is that the Four Site?
VICE CHAIRMAN WYMER:
I picked up on it
somewhere.
18
MR. PHILIP:
I'm Jake Philip with the
19
Office of Research and one of the things we are
20
looking with NIST, the National Institute of Standards
21
and Technology is you know if you have a concrete
22
structure and you want to entomb it, what you really
23
need to look at, how does it perform a condition
24
assessment of the structure?
25
such thing as a Commission assessment of a structure
Right now, there's no
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like a concrete containment building.
2
even entomb, you've got to know the quality of the
3
structure.
4
So before you
How good is it?
And then you've got to know if -- well,
5
most
of
6
observational.
7
problem is actually the cracks in the concrete that
8
would be the most important aspect as far as risk from
9
an entombed facility.
10
the
ways
to
look
at
it
is
mostly
And we find from a flow and transport
So then we have to look at how the cracks
11
form, are they all the way continuous.
If it's
12
continuous, that's the problem. However, we feel that
13
in a concrete structure, as massive as a containment
14
structure, it probably will not have cracks like that.
15
But that's something we have to look for. And once we
16
look for that, then the next question is are there
17
some ways to look at other imperfections in the
18
concrete, looking at the joints, looking at maybe
19
segregation of the aggregates in the concrete and
20
stuff like that, having many instances of some types
21
of bad concrete.
22
So we were looking at some destructive or
23
nondestructive ways, actually to basically get the
24
baseline data on the containment structure before --
25
the entombed structure before we really go and entomb
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it.
Of course, the next point is we have all that
2
information as far as modeling of the concrete for
3
flow and transport and stuff like that, but we don't
4
have any experience on how well they perform or what
5
time. So then can that be a modeling program? That's
6
one of the things we look now -- a modeling program
7
which
8
performs and then verify some of the models that we
9
have used in making the predictions.
could
look
at
how
the
10
DR. BAHADUR:
11
VICE CHAIRMAN WYMER:
concrete
structure
Excuse me -Somewhere in this
12
presentation I put some of this flood of paper that we
13
get -- I read something about that, about what he just
14
said.
15
I want to make one observation here for
16
whatever it's worth.
There's -- it seems to me
17
there's a problem with the greater than Class C waste
18
in that we have two kinds which are very different in
19
kind and they're both greater than Class C.
20
the sealed sources which is well-defined situation.
21
You have a sealed source.
22
trash that comes out of decommissioning reactor which
23
is greater than Class C and it's certainly not sealed
24
in any sense of the word.
25
thought ought to be given to separating these two
One is
The other though is this
So it seems to me that some
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1
kinds of greater than Class C waste in how they're
2
handled or in how they're regulated or something,
3
since they are so very different, different in kind.
4
That's just an off the top of my head observation.
5
Any
other
questions
or
comments
from
6
anybody?
7
look forward to your next progress report, probably in
8
October or some time following that.
9
10
DR. BUSH-GODDARD:
I don't know.
We
We'll
keep the staff informed, I guess.
11
12
If not, thank you very much, Stephanie.
VICE CHAIRMAN WYMER:
Thank you.
Here's
CHAIRMAN HORNBERGER:
Thank you, Ray.
George.
13
We
14
have about an hour and 5 minutes before our scheduled
15
next thing on the agenda.
16
from recording?
17
take a break for -- we'll pick up recording after our
18
coffee break.
Do we want to take a break
We're going to discuss -- so we can
19
(Off the record.)
20
CHAIRMAN HORNBERGER:
The meeting will
21
come to order.
22
behavior of waste packages and the ACNW Member leading
23
this discussion again will be Ray Wymer.
24
the meeting over to Ray.
25
Our next session is on the long-term
VICE CHAIRMAN WYMER:
I'll turn
Thank you.
We're
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1
welcoming these presentations this afternoon.
2
waste package remains the central issue with respect
3
to the repository performance and this morning and
4
into this afternoon, we're going to hear presentations
5
from David Esh and Tae Ahn and the first presenter
6
will
7
performance assessment perspective on the behavior of
8
engineered
9
emphasis on waste packages and risks associated.
be
David
Esh
barriers
who
and
will
in
be
talking
particular,
The
about
with
the
10
Dave?
11
DR. ESH: Thank you, Dr. Wymer. I'm David
12
Esh.
13
Environmental and Performance Assessment Branch and
14
I'm here to talk about the PA perspective on the
15
behavior of engineered barriers.
16
I'm
a
System
Performance
Analyst
There are many contributors.
in
the
The main
17
contributors for this presentation were Dick Codell
18
and Sitakanta Mohanty, but I could pretty much list
19
everybody that contributed at some level to the PA
20
work.
21
(Slide change.)
22
DR. ESH:
My basic outline and the main
23
points that I wanted to cover in this presentation are
24
summarized here.
25
The
overall
repository
risk
with
our
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1
current knowledge, it's kind of a snapshot in time and
2
then I'm going to talk about insights on system
3
behavior and waste package as a barrier.
4
salt barrier?
Is it the
5
And then an issue that the Committee has
6
raised in the past, conservatism and risk, I'm going
7
to cover that with, I think, an insightful example and
8
explain how that can be problematic and how we deal
9
with it.
10
And then I'm also going to talk about the
11
main
focus
of
this
presentation
as
our
PA's
12
perspective on the waste package key issues and that
13
leads into Dr. Ahn's presentation where he'll cover
14
those key issues in depth.
15
So I'm kind of giving you a step in from
16
the top down working towards the waste package key
17
issues and giving you some insights along the way.
18
Now our perspective comes from a lot of
19
different things.
20
independent analyses that we do, both at the NRC and
21
at the Center for Nuclear Waste Regulatory Analysis.
22
And that independent analysis takes the form of a
23
number
24
Performance Assessment Code, TPA Code, which we're
25
currently in development of version 5.0; uncertainty
of
One of the main things is our
different
things.
The
Total
System
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1
and sensitivity analysis.
I believe our report is
2
being worked on right now in that area that contains
3
a lot of -- it's my sales pitch, a lot of useful
4
information.
5
and then other which can take any number of forms,
6
simple calculations to all sorts of auxiliary analyses
7
that we do.
8
-- besides our independent work, the review of what
9
the Department of Energy does and others, EPRI, the
10
State of Nevada, all of that conditions are thinking
11
and here's my gratuitous suck up. The comments of the
12
Review Committees which I've listed, ACNW and NWTRB
13
peer reviews.
And it also includes barrier evaluation
And our perspective is also a result of
14
Seriously, all of that -- sometimes you
15
need other perspectives and those other perspectives
16
can be very useful and so all of that conditions are
17
thinking.
18
assessment is not just putting things into a code and
19
getting things out.
20
those results, how things are functioning, why they're
21
functioning
22
objective.
23
presentation that that's one of the key things that we
24
do in performance assessment is try to understand
25
things and try to interpret things, not just generate
But my main point here is that performance
the
And
It's understanding why you got
way
so
they
I
are.
hope
That's
you
get
our
main
from
this
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1
results.
2
(Slide change.)
3
DR. ESH:
So starting at the top, a
4
summary of where we are right now is DOE results for
5
the repository risk and also the failure of the
6
packages and I'll summarize this verbally in the next
7
slide, but what I want to emphasize is that we have
8
various risks, depending on the time period and we
9
have a nominal scenario and an igneous scenario and
10
that
the
risks,
while
proportional
to
failures,
11
failures might not be a good metric to think of in
12
terms of risk and hopefully you'll see that in some of
13
the slides going forward.
14
Certainly, the risks get larger as these
15
packages failed, but it's not just failure that's
16
important.
There's other things to consider.
17
(Slide change.)
18
DR. ESH: The overall repository risk, our
19
current understanding, the 10,000 year model risks are
20
small and I'm careful here to say model risks.
21
think we have to understand that we're simulating this
22
problem and that's the best that we're ever going to
23
be able to do.
24
that
25
uncertainties.
our
I
And assuming, the caveat is assuming
current
model
appropriately
represent
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1
The longer time risks are comparable to
2
background radiation.
Igneous model risks are larger
3
than
but
4
standard.
5
this is the case, what are we doing?
Why are we
6
continuing to look at this problem.
I tried to
7
summarize that in the next slide because we have some
8
key uncertainties that we're evaluating. Some of them
9
are subject -- represented in the agreements between
10
NRC and DOE that we want to see the impact of those
11
uncertainties on the timing and magnitude of the doses
12
and
13
disruptive
14
important and occurs early in the 10,000 year period
15
and the capabilities are the barriers.
16
these uncertainties.
17
because we want to evaluate the impact of those
18
uncertainties going forward.
nominal
the
risks,
small
compared
to
the
So I look at this and I saw well, okay, if
nominal
doses
scenario,
because
the
the
magnitude
timing
of
isn't
the
very
So we have
We continue to do analysis
19
(Slide change.)
20
DR. ESH: Now that's kind of a snapshot of
21
what we have right now, the way -- if you look at the
22
way the repository system is working, that's the main
23
overall result.
24
down and we say this repository is made up of many
25
things that we're you're all aware of and what I want
But now let's go down into one layer
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1
to stress is not all of these things are created equal
2
from a risk perspective.
3
important, some of them are less important.
4
expected in a system like this, complicated system
5
with lots of parts.
Some of them are more
That's
6
And both NRC and DOE analyses -- I think
7
there are some backup slides, suggest that waste
8
package performance is a significant contributor to
9
limiting future risk and we're here today to talk
10
about the waste package and I think it's appropriate
11
to spend significant amount of time talking about
12
waste package issues in detail.
13
Within performance assessment and I think
14
throughout
the
15
calculations
16
insightful.
17
complicated models and doing complicated analysis and
18
sometimes you can do some pretty simple things that
19
you can learn a lot about how the repository system is
20
working and why.
that
program,
we
think
we
can
complete
be
simple
particularly
Sometimes we get caught up in building
21
And so in this overall system, you've
22
heard some opinion that the waste package is the only
23
barrier, it's the only significant thing.
24
trying to -- I asked that question and I try to answer
25
it on the next slide, at least from one viewpoint.
Well, I'm
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1
(Slide change.)
2
DR. ESH:
With any of these difficult
3
problems, you can do different analyses and they may
4
tell
5
important to do a variety of analyses. This is a very
6
simple calculation where you just take the inventory
7
of the iodine and technetium that's in a commercial
8
spent nuclear fuel package, those are the readily
9
transported species.
you
different
stories,
but
that's
why
it's
Now let's just assume that the
10
best you can do with the rest of the system is you can
11
have some distributive failure, the waste form lasts
12
some time, the cladding lasts some time, but it's only
13
equivalent to about 500 years, a very short period of
14
time.
15
You dilute that release in the regulatory
16
defined water volume and you get a dose from a single
17
package of about half a millirem a year, that's from
18
a single package.
19
Now if you compare that to say the TPA 4.1
20
result which has approximately 40 initial failures,
21
you have a dose of .02 millirem per year.
22
you look at these two numbers and the fact that this
23
is 40 failures and that's a single failure, the
24
results are that the TPA 401 results are about a
25
factor of a thousand lower.
Well, if
So if you're trying to
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1
argue that well, the waste package is the only thing
2
that matters in this system, I would say I don't think
3
so.
4
contribute. Sure, it plays a very important role, but
5
there are a lot of other things that contribute -- if
6
the other things weren't contributing, you couldn't
7
have this disparity in numbers like you do here.
8
you can do various other comparisons, but they all
9
come
10
I think there are a lot of other things that
out
pretty
much
the
same
way.
So
And
other
components greatly influence the future risks, too.
11
So we have the repository behavior.
We
12
have the waste package within the repository and now
13
we're getting into what are the mechanisms and the
14
processes that affect the waste package and the tact
15
that we took here was to look at risk and surface
16
area.
17
processes may be more important than others? And why?
18
Well, the risk and surface area failed,
19
the two main release mechanisms are diffusive or
20
vective transport with the water.
21
are proportional to the surface area of the failures,
22
directly.
23
correlated because you could say that they're also
24
directly proportional, but it gets more complicated
25
than that as the system state degrades, you run into
So
okay,
which
corrosion
mechanisms
or
Diffusive releases
Advective releases are at least strongly
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1
shedding on the surfaces of the packages, so as you
2
have initial fail package that might have one hole in
3
it, the water that drips on the package can run into
4
that hole and it's not just a direct surface area
5
scaling that creates the results in the releases and
6
dose.
So it's a little more complicated, but it's at
7
least
strongly
8
failed.
correlated
with
the
surface
area
9
What I attempt to do in the upcoming
10
slides are to look at well, does the type of failure
11
have a strong influence on the risk or do you just
12
need failure, any sort of failure, or are they all
13
equal?
14
(Slide change.)
15
DR. ESH:
And this figure on Slide 10 is
16
some information extracted from the DOE TSPA-SR median
17
value file.
18
presentation and maybe you also see in the future,
19
that we're going to be doing more work analyzing and
20
reviewing
21
working, why it's working, what issues we identify and
22
those sorts of things. We have a number of activities
23
that are on-going along those lines, for instance, I
24
think Tim McCartin is leading an activity to produce
25
a comparison of TPA code results to DOE's TSPA model
DOE
And I think what you'll see in this
and
explaining
how
their
model
is
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1
results and see how the various models compare and
2
differ. I'm leading an effort to review DOE's TSPA-SR
3
model and Goldsim to build up our capability and
4
understanding of the Goldsim software and also to
5
understand how their model is working and what it's
6
doing.
7
This figure is basically -- the pink curve
8
here is the crack area, so it's the total cumulative
9
area from crack failures in a package.
It starts at
10
slightly less than 40,000 years.
The blue curve is
11
the cumulative patch failure area per package and the
12
red curve is the technetium 99 dose.
13
Now what you see is that the cracks start
14
earlier. They have a more gradual slope. The patches
15
come in in this median value file at about slightly
16
around 65,000 years.
17
responds pretty directly.
18
failures start exceeding the crack failure area, the
19
dose increases rapidly. And what this says is that at
20
least at early times, the risk is proportional to
21
surface area failed.
But if you look at the dose, it
As soon as those patch
22
Now in DOE's model at about 65,000 years
23
where there's only cracking existing for the median
24
value file results, they have a dose of about .3
25
millirem for technetium from 20 cracks per package.
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Now what I want to show is that okay, if
2
the risk is proportional, the surface area failed,
3
what else is important when you're trying to assess
4
waste package failure?
5
And what we did was we looked at the
6
diffusive risks from stress corrosion cracking, so
7
right now in the TSPA-SR, the cracks only form in the
8
end cap areas, the welded areas of the end caps and we
9
did two models here. One, we did a conservative -- we
10
should
probably
use
pessimistic
representation.
11
Conservative is a difficult terminology, where we
12
diffused through the end caps and what we did is we
13
took the inventory of iodine technetium neptunium
14
that's inside the package.
15
release.
16
Diffused it through the end cap and then assumed a
17
zero concentration boundary on the outside because of
18
water flowing that could release it.
19
model such as that, you'd get a result of about 300
20
millirem per year from 300 cracks and a thousand
21
packages, fairly large number.
We made it available for
We put it at the opening of the crack.
If you did a
22
But our concern was well, okay, is your
23
conservatism influencing, greatly influencing your
24
conclusions here? And would it cause you to judge the
25
importance of a corrosion mechanism different than
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maybe what you should?
2
well, the fuel inside of the package, especially for
3
the state when you have a package, it's only cracked.
4
You get a water film on the inside of the package, but
5
otherwise
6
outflux of moisture into the system.
there's
no
So what we did is we said
inflow,
there's
no
influx,
7
The fuel that fails inside the package,
8
the radionuclides have to diffuse from that fuel to
9
the point where the cracks are in the lid.
And that
10
water film is very thin, or at least the information
11
that
12
suggests that it will be very thin.
we
were
able
to
get
out
of
the
literature
13
When you take into account the diffusion
14
through the water film to get to the end caps and then
15
model
16
performance benefit from the rest of the repository so
17
you
18
processes, but you still dilute it in the regulatory
19
defined water volume, that reduces the dose to a
20
fraction of a millirem.
21
have to be really careful and I think the Committee
22
said something along these lines in one of their
23
letters.
24
using conservatism and from a regulator's standpoint,
25
we have to be careful when we interpret the results of
it
the
neglect
same
the
on
the
unsaturated
outside,
zone,
and
take
saturated
no
zone
So my conclusion is that you
You have to be really careful when you're
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1
highly conservative models.
2
I guess what I'm trying to stress is that
3
we, within performance assessment do a lot of things
4
like this to try to understand the implications of
5
that conservatism.
6
Now it's up to the Department of Energy to
7
choose, if they want to use a conservative model they
8
can use a conservative model and we have to review
9
that conservative model, but we should understand the
10
implications of the use of that conservative model if
11
it creates other sorts of problems.
12
I wanted to highlight is what we attempt to do.
And that's what
13
So the failure mechanisms, whether it's
14
cracks or patches or pits or whatever, it can be
15
influenced by what you're doing elsewhere in the
16
model.
17
conservative for the transport, or release and/or
18
transport, then you may be somewhat misled about the
19
importance of failure versus type of failure and let's
20
see -- so you need to be cautious, especially when
21
you're employing conservatism in the mass transfer
22
representations. The waste package failure mechanisms
23
that result in numerous small openings or a few
24
catastrophic
25
significant and I'll go through those in a little more
In this case, if you're doing something very
failures
are
not
likely
to
be
risk
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1
detail in upcoming slides.
2
From a PA standpoint, I'd say the staff
3
are most concerned with mechanisms that may result in
4
numerous, moderate to large openings that experience
5
avective conditions.
6
this problem.
7
That's the real risk driver in
Now okay, based on what I said about
8
failure
types
and
how
9
performance assessment went through and we give our
10
perspective on these issues that Dr. Ahn is going to
11
cover in detail and these nine issues are subject
12
areas where you could spend an hour or two hours on
13
each one if you wanted to and so I want to try to give
14
as much time for Tae and the Committee to evaluate
15
these as you would like today.
16
(Slide change.)
17
DR. ESH:
it
affects
risk,
then
From a PA perspective, the
18
environmental
conditions,
uniform
corrosion,
19
passivity, localized corrosion, materials aging, those
20
are all things that together or in a synergism or by
21
themselves could result in the numerous, reasonably
22
sized openings. Now I say could here and what I think
23
Tae is going to cover is that this could, should be a
24
different sized font for each of these.
25
really big for one of them. It's more likely to occur
It might be
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1
and for some of the other ones it's less likely to
2
occur.
3
And
it's
important
to
understand
the
4
consequence and identify the likelihood of this trans
5
passivity localized corrosion phenomena.
6
I guess performance assessment also has
7
some
perspective
on
the
environmental
conditions
8
because that is a particularly difficult area to
9
evaluate the uncertainty.
It comes from a lot of
10
different sources and when you consider the chemical
11
divide process, a small uncertainty upstream can be
12
propagated into a big effect downstream.
13
really difficult to evaluate the uncertainty and the
14
environmental conditions and I think for many of these
15
-- or at least for some of these major corrosion
16
mechanisms or processes, they're influenced strongly
17
by environmental conditions and especially extreme
18
environmental conditions.
19
strong job on the uncertainty evaluation for the
20
environmental conditions.
21
22
Stress
So it's
So it's important to do a
corrosion
cracking
is
what
I
covered in Slide 11.
23
Now it looks like the frequency and the
24
size of the openings are not likely to create a
25
significant risk, and I use that term loosely, unless
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1
combined with conservative release modeling.
2
do
3
conclude that the stress corrosion cracks are more
4
important than what they are.
conservative
5
Now
release
I
would
modeling,
note
that
then
the
If you
you
can
advective
6
releases are not expected for the cracks, based on
7
their size and the capillarity argument.
8
the size of the crack is so small it acts like a pore
9
and the capillarity pressure wants to hold water in it
10
and you don't get enough of a driving force to move
11
any moisture -- to effectively flow moisture through
12
that crack.
13
Now,
there
is
an
Basically,
uncertainty
in
the
14
pessimistic side that maybe these cracks grow once
15
they form -- they continue to get bigger, and that
16
would influence the release. There's uncertainties on
17
the optimistic side that the cracks can arrest. Right
18
now the cracks, once they begin growing, they continue
19
to grow, but I guess that's observed that many times
20
these cracks arrest and they don't propagate the whole
21
way through the surface.
22
plug with corrosion products.
And also, the cracks can
23
So any of these things that we're doing a
24
perspective on now have an uncertainties associated
25
with them.
I think that Tae is going to cover a lot
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1
of those uncertainties in greater detail.
But this
2
stress corrosion cracking we would say is somewhat of
3
a lower risk significance.
4
Drip shield performance, if we were purely
5
running a code and looking at results and not doing
6
any thinking, we would probably say is a lower risk
7
significance.
8
couple back up slides, one that DOE did, barrier
9
degradation or subsystem degradation, and you can look
10
at the difference between the drip shield one and the
11
waste package one and say well, waste package isn't
12
doing anything.
13
package may be preventing rockfall damage or other
14
mechanical damage to the waste package.
15
also be preventing aggressive chemical conditions for
16
the waste package that would lead to some of these
17
failures that we would judge as more risk significant.
18
So from a thought standpoint, you might
19
conclude that the drip shield serves more of a role
20
than
21
standpoint. Now you could argue that well, if you put
22
those things in your model, you should be able to do
23
analysis that the function of the rockfalls or the
24
aggressive chemical conditions, the function of the
25
drip shield preventing those should show up in your
what
I think there's a back up slide, or a
But if you think about it, the waste
you
would
get
from
a
And it could
quantitative
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1
analysis.
You should be able to do something, and I
2
think that's probably true.
3
something,
4
standpoint saying well, it could be important, from a
5
more quantitative standpoint be able to show okay,
6
here's why it would show up as important or more
7
important.
that
instead
You should be able to do
of
just
from
a
thought
8
Mechanical failure, our current analysis
9
suggests that the combination and the likelihood and
10
the consequences, or I should say DOE's analysis are
11
a lower risk. The extent of the drift degradation and
12
the resultant consequences need to be further analyzed
13
however,
14
significance,
15
anywhere from low to high depending on the extent and
16
the likelihood.
17
very little drift degradation and in the TSPA-SR, if
18
you just looked at those results, you would say it's
19
a lower risk significance.
20
peer review panel that kind of expect significant
21
drift degradation and also the NRC and CNWRA staff
22
have a number of concerns about the uncertainty in
23
that area.
so
that
but
rockfall
the
drift
is
a
lower
degradation
risk
could
be
Now, in the TSPA-SR, they simulated
But I guess there is a
24
Juvenile failures, you can look at the
25
results on Slide 4 and 8 and you can see that the
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1
frequency is not high enough to create a significant
2
risk.
3
criticality is complicated, it's coupled to a lot of
4
things, it's related to the geochemistry inside the
5
package and water flow. But current analyses suggests
6
the
7
significant risk.
8
item.
It's a lower risk significant item.
likelihood
is
not
large
enough
to
And
create
a
So it's a lower risk significance
9
Now, the Committee, I think, always asks,
10
maybe you don't want to hear about it, but you always
11
ask about risk informing.
12
giving a little performance assessment perspective on
13
it.
14
abstraction, which is how you build models, treat
15
uncertainty, the confidence in those models.
It's
16
TSPAI
with
17
uncertainty.
18
to uniform corrosion, passivity, localized corrosion,
19
and environmental conditions, the things that, we
20
feel, are more risk significant from an uncertainty
21
standpoint.
22
Maybe
23
informed.
We
42
sub-issue
you
24
25
have
And this is my stab at
agreements
3.
Many
related
of
those
to
model
deal
Well, about 30 percent of them pertain
So I can only say we're consistent.
could
argue
we're
not
still
not
risk
But at least we're consistent.
So
in
summary,
waste
package
is
an
important barrier, but it can do some simple things
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1
and even more quantitative things, results which are
2
shown in the back up slides that you can conclude the
3
performance of other system components limit risks.
4
You need to be really careful with the conservatism,
5
because that greatly influences your interpretation of
6
the problem and the work that you do.
7
I think the PA results and additional
8
analyses condition our thinking, but we do a lot of
9
thinking outside of our analyses.
And we do lots of
10
different analyses to get different perspectives.
11
Depending on your analyses, you can have different
12
views and you want to be careful about the conclusions
13
that you make.
14
And
my
last
bullet
is
the
assigned
15
relative risk importance to CLST issues is based on
16
current
17
[nothing], we can be wrong, and we'll talk to you
18
about it in the future, I'm sure, if we end up being
19
wrong about one of these things.
20
VICE CHAIRMAN WYMER:
understanding,
so
that's
my
caveat
that
So that's it.
Thank you.
I had
21
one question, David, on Slide 8, which deals with
22
waste packages of barrier and you take inventory of
23
one particular fuel waste package and you somehow
24
relate that what the results of TPA 4.1.
25
quite make the logical connection.
I can't
Is TPA 4.1 give
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1
you a thousand-fold lower result for waste package
2
because you simply don't dump the entire inventory?
3
DR. ESH: That's what I guess I was trying
4
to say.
There are a lot of things that cause that
5
risk to be lower than you would get if the waste
6
package was the only thing. Waste form, which results
7
in distributed release; cladding, which results in
8
distributed release; the solubility limits, which
9
changes the magnitude of the release, which I guess
10
you could say distributes it.
11
transport precesses through the UZ and the SC, that
12
for
13
technetium, might not have a huge influence from
14
retardation.
15
during those transport processes.
readily
16
transported
And then the whole
species
like
the
iodine
They still have dispersion and dilution
There's a number of other things in this
17
repository system that change those numbers.
18
that's what I wanted to say, is that if you're trying
19
to make the argument, well, the waste package is the
20
only thing, and that should be our complete emphasis,
21
you're missing the story that this a system model and
22
a lot of things contribute.
23
VICE CHAIRMAN WYMER:
24
the message I got.
25
take a simplistic approach.
And
That's not exactly
The message I got was that don't
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1
DR. ESH:
Also, I think the simplistic
2
approaches can be used to -- I think they're useful
3
when you're trying to get an unconfounded perspective
4
about some of these simple processes.
5
how we like to use them as they can go a long ways and
6
they're pretty easy to understand.
7
8
I think that's
VICE CHAIRMAN WYMER: Okay, any questions?
Milton?
9
DR. LEVENSON:
I just have one comment.
10
I think if you sat in on any of the meetings of this
11
Committee in the last year -- glad to see that your
12
statement that be careful about the use of the word
13
conservative,
14
because it can mislead you badly about what's going
15
on.
16
and
don't
DR. ESH:
overstate
consequences,
You can imagine that if you did
17
something really conservative on your model, and then
18
you go away and forget about it.
19
it's conservative, but you never look at it in more
20
detail, it can be difficult to interpret your results
21
than in a risk informed manner.
22
VICE CHAIRMAN WYMER:
23
CHAIRMAN HORNBERGER:
Or you say, well
George.
Dave, in terms of
24
CLST, currently is your view that the TSPA insights
25
are similar, or essentially the same, as the TPA
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1
insights?
2
DR. ESH:
For a large part, I think.
I
3
think, because we don't perceive that we have such a
4
pessimistic release model, we may have a greater
5
tendency
6
important, and it's partly because it's a system model
7
and it's one of the first things in a sequence of
8
things that operates.
9
if
10
it's
to
--
we
preforming
still
believe
CLST
is
very
So when you see your results,
a
big
function
that
greatly
influences your results.
11
I
think
we
view
the
CLST
as
a
very
12
important issue.
We also believe that NTPA, we have
13
some work to do with representing some of these
14
processes and uncertainties and that's ongoing in TPA
15
5.0.
16
in
17
failures from realization to realization, but we don't
18
distribute them within a realization. But I think, as
19
Dick Codell talk to you in the past, we've done a lot
20
of off-line analysis to look at the implications of if
21
you distribute your failures within a realization,
22
package to package, patch to patch, and what are the
23
influences of those processes.
We don't distribute our failures, for instance,
the
sense
that
DOE
does.
We
distribute
our
24
So I think there are, Tae can talk to it
25
in more detail, because he has a lot of the details
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1
even in back up slides, of what the TPA code is
2
producing and you can compare that to what DOE's model
3
is
4
corrosion, for instance.
producing
for
various
processes
like
uniform
5
NTPA, we didn't have the stress corrosion
6
cracking model, and I don't know if Chris Grossman is
7
here, whether we're going to do it for TPA 5.0 or not,
8
because
9
circumstances could you have a significant risk from
it
looks
to
us
like
only
in
special
10
it.
In TPA 5.0 or in the TPA code, we originally had
11
a diffusive release model, and then we took it out
12
because
13
significant risks from the diffusive releases. Now we
14
think we're going to put it back in just so we can
15
have the flexibility to analyze these different cases
16
if someone chooses to be conservative with release
17
modeling for instance.
it
looked
like
we
weren't
getting
any
18
So I think in general, there aren't wide
19
differences, but adding any sort of these phenomena
20
with the detailed uncertainty is difficult in these
21
models and it takes time.
22
off-line analyses to look at the uncertainties rather
23
than immediately, explicitly adding things into code.
24
Whereas
25
processes or phenomena directly into their performance
DOE
may
go
right
We try to do a lot of
to
the
root
of
adding
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1
assessment model.
2
CHAIRMAN HORNBERGER:
Let's see.
The
3
second question.
4
you're doing, the approach that you're taking, taking
5
will lend itself to assisting in a potential license
6
application
7
hypothetical, where DOE has some of these things in it
8
that are what we might call, I think your term, overly
9
pessimistic, instead of conservative.
10
in
Do you think that the work that
the
situation
and
we'll
be
And it can
color the interpretation.
11
Do you think that your approach will allow
12
you to sort of disentangle it and still make some
13
risk-informed judgments?
14
15
Or, do you think it will be buried in the
TSPA?
16
DR. ESH:
I think it can be useful.
I
17
can't say whether it will be useful.
18
on the specifics of their performance assessment,
19
going forward.
20
It will depend
But I think it's something you have to
21
attempt, at least.
22
the effects of, say, the conservatism is so that you
23
can try to make those risk-informed judgments.
24
don't know.
25
You have to try to unravel what
CHAIRMAN HORNBERGER:
I
Again, probably an
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1
unfair question for you, perhaps.
2
that in looking at the Yucca Mountain review plan that
3
the
4
confident that you would be able to at least take the
5
first steps to do the disentangling?
acceptance
6
criteria
are
But do you think
such
that
you
feel
DR. ESH: Yes, I think -- I can't speak to
7
the review plan directly.
I think there's somebody
8
probably here who could.
9
the work that we do, it would be difficult to like
10
make an acceptance criteria or a review method to say
11
okay, you do this or you do that.
12
philosophy of how do you handle this sort of problem
13
and the sorts of issues that we are dealing with.
But I can say that a lot of
It's more of a
14
Maybe at a higher level, you should have
15
some direct language that would speak to that, but
16
it's really -- I mean their viewpoint is pretty
17
extensive as it is and I think if you tried to put all
18
of that in it directly it would be very cumbersome.
19
CHAIRMAN HORNBERGER:
Thanks.
20
VICE CHAIRMAN WYMER:
John?
21
MR. McCARTIN:
Tim McCartin, NRC staff.
22
In terms of the review plan, certainly the desire is
23
that -- and we will understand DOE's performance
24
assessment.
25
put in there, there's that sort of tug between too
As Dave indicated, how much detail you
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1
much detail and conveying a message without having to
2
reach 50 pages.
3
But
4
understand
5
assumptions.
6
without
DOE's
models
question,
and
we
have
understand
to
their
And I think we will.
One
of
the
things
Dave
did
very
7
effectively here is, try to put a quantitative value
8
on a potentially pessimistic model for release.
9
he had a good way to quantitatively give a sense of
And
10
gee, we think this is pessimistic.
11
does it have?
12
number on how pessimistic this is?
13
key models, yes.
14
if we feel they supported, -- this is conservative, we
15
won't necessarily try to quantify everything.
16
might be a daunting task. But we certainly would have
17
to understand, whether the information supports it
18
being conservative.
19
How much effect
Will we have to quantitatively put a
I think for the
But all of them, some things, well,
MEMBER GARRICK:
That
Dave, it seems as though
20
you're taking steps toward something that we've been
21
interested in commenting on for a long time and that
22
is begin to decompose this problem into some first
23
principles that are comprehendible.
24
looking
25
inventory that you have to worry about in that waste
at
an
individual
waste
And the idea of
package
and
the
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1
package and the case, in your case here, technetium
2
and iodine, but you could also add the only other
3
things
4
actinides, neptunium and plutonium.
that
we
have
to
worry
about
such
as
the
5
I think this is very important that you
6
kind of start out with something so basic as a waste
7
package and what are the bad actors that we have to
8
worry about, and then begin to put filters on those in
9
terms of the waste package and then the natural
10
setting that begin to communicate in a kind of a first
11
principles way the activities and the barriers that
12
this stuff goes through as a function of time and the
13
effectiveness of each of those filters.
14
I
just,
I
guess
this
is
partly
a
15
compliment that this is the kind of the first time I
16
began to see something that we've been alluding to for
17
a
time
to
18
communication
of
19
principle's physics model.
20
see the same thing beyond the waste package in terms
21
of
22
regions of the natural setting, the contribution of
23
retardation and the effect of dilution and the effect
24
of
25
rainfall, if you wish, to biological uptake.
long
the
help
building
contribution
uptake
to
the
the
from
point
whole
a
issue
kind
of
or
a
risk
first
It would be very nice to
dispersion
where
we
in
different
really
go
from
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1
So I think this kind of thought process is
2
very effective.
3
almost imagine a schematic here, based on a source and
4
these
5
through
6
radionuclides that you have to worry about.
7
as if you have to worry about 51 actinides and 250
8
fission products.
9
four.
10
multiple
these
I think the thing that you could
barriers
and
barriers,
the
this
idea
of
limited
tracing
number
of
It isn't
We're only worried about three or
So that's very positive and I would encourage
you to continue to do this.
11
I think also it's very important to keep
12
the focus on the whole notion of what is meant by
13
risk.
14
Risk is risk.
15
notice
16
distinctions. I think that the one thing that we want
17
to always, it seems to me, start from is what we
18
actually thing is the risk, rather than a conservative
19
risk or a modified risk or a qualified risk of some
20
sort.
Risk is not conservative or non-conservative.
you're
And so I think that when -- and I
beginning
to
draw
those
kinds
of
And go from there.
21
I think that the ability to begin to sort
22
out where contribution is coming from in terms of
23
performance
24
reassuring everybody that there is performance role
25
here for all facets of the repository and we need to
is
going
to
go
a
long
ways
toward
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1
-- we need to quantify that role and we need not to
2
get ourselves in the position where we're necessarily
3
conveying that one barrier is all we really need or
4
whatever, but lay it out in terms of well, this is
5
what the contribution to performance is from the
6
various barriers.
7
So I think this is good stuff. As long as
8
we don't lose sight of characterizing it in a simple
9
form as possible and as long as we don't lose sight of
10
what we mean by risk.
11
DR. ESH:
I encourage us to continue.
I think we have a tendency to
12
want to impress you with our complexity and sometimes
13
it can be problematic from a communications standpoint
14
and it can be problematic from a human intellect
15
standpoint of interpreting exactly what did I get and
16
why?
17
So one of the functions that we have to do
18
in
performance
19
reasonableness of DOE's performance assessment model
20
and I believe an easy way to do that is to do these
21
sorts of simple calculations and see how the simple
22
calculations compare to that complex model or how they
23
differ and then you can start extracting, excuse me,
24
why they differ.
25
assessment
is
evaluate
the
MEMBER GARRICK: Yes, and I think that you
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1
can get to a point where you can answer the kind of
2
questions that Ray asked about the difference between
3
the two values on Slide 8 very easily, that this is a
4
direct
5
associated with barrier D that contributes the most is
6
dispersion.
result
of
barrier
7
DR. ESH:
8
MEMBER GARRICK:
D
and
the
phenomena
Sure.
And once you get to a
9
point that you can begin to present the information in
10
those terms, then I think it really begins to be a
11
powerful way to communicate.
12
13
VICE CHAIRMAN WYMER:
Any questions from
the staff?
14
MR.
CAMPBELL:
This
whole
use
of
a
15
diffusion model by DOE actually goes beyond the stress
16
corrosion cracks.
They actually use it for the
17
patches
model
18
corrosion on the waste package.
19
later time frames, it is the major release mechanism
20
for TSPA-SR.
21
packages never see advective flow, never see flowing
22
water.
23
a water film.
that
they
developing
from
general
And in fact, even at
Eighty seven percent of the waste
They just simply see essentially humidity in
24
And throughout TSPA-SR, DOE says they're
25
modeling the flow or attempting to address the flow of
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1
water over a film.
2
shown is their model, in fact, grossly overestimates
3
the potential release, that as a potential release
4
mechanism.
5
that
6
environment and it's in this big long report that was
7
issued a year ago.
8
identified
9
identified this as a potential problem.
we
10
And I think what you guys have
We identified that in our own analyses
did
for
this
waste
package
in
near-field
The international peer review
as
a
problem.
I
think
DOE
has
Do we have any indication that they're
11
actually going to do something about this?
12
come up with a more realistic model for their source
13
term release?
14
DR. ESH:
I don't know.
And maybe
I know we've
15
talked to them about it a number of times and I can't
16
say what their plans are.
17
evaluating it.
18
MR. CAMPBELL:
I think they're certainly
Are there -- and a second
19
apart of that question, are there potentially negative
20
impacts on the concept of a multiple barriers approach
21
if, for example, they stick to a very conservative
22
release model?
23
DR. ESH:
I think so.
I think you could
24
short change yourself if you're doing something very
25
conservative that influences your perspective of how
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1
the overall system works.
2
For instance, if you had the -- say you
3
had a failure mechanism that the end cap fell off the
4
package and you had an opening.
5
occur through that whole geometic surface area.
6
occurs through the water films that will be contacting
7
that circumference.
8
can get much different results.
9
careful about it.
Diffusion doesn't
It
So depending on what you do, you
You just have to be
10
Slide 22, by the way, is your test, if you
11
want to look at that and try to explain what the three
12
bumps are from.
13
14
So you can look at it and then talk to me.
I'll tell you if you're right or not.
15
(Laughter.)
16
VICE CHAIRMAN WYMER:
Are there any other
17
comments, especially from over here on my right?
18
Observations or questions?
19
Okay.
Well, thank you, Dave.
20
MS. HANLON:
21
VICE CHAIRMAN WYMER:
22
MS. HANLON:
Dr. Wymer?
That was Carol.
Hi, this is Carol Hanlon.
23
I'd just like to respond to Andy.
24
that
25
evaluations are higher and we are looking at that and
we
had
noticed
is
that
One of the things
our
models
and
our
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1
calculating it and intend to correct it.
2
Abe was going to try and be here to today
3
to speak to that point, but he's caught across town.
4
But we are aware of those differences and looking to
5
adjust them.
6
VICE
CHAIRMAN
WYMER:
That
was
Carol
7
Hanlon.
8
importance and although not necessarily overriding
9
importance, although it's front and center right now.
10
We're going to hear from Tae Ahn about the
11
present status of issue resolution and risk assessment
12
and waste package and drip shield performance.
13
Well, as we've seen the waste package is of
DR. AHN:
Thank you, Dr. Wymer.
Dr. Esh
14
introduced to you the importance of waste package risk
15
domain.
16
failure modes of waste package and drip shields.
I would like to go over in detail all the
17
Many of the staff members of the NRC and
18
the Center participated in the performance assessment
19
of
20
Container Life and Source Team, KTI is the lead KTI,
21
led by Tammy Bloomer, Gustavo Gragnolino and Vijay
22
Jain. And we also have participants from total System
23
Performance Assessment Integration KTI, IDTME and
24
Evaluation of Near-Field Environment KTI.
waste
25
package
and
drip
shield
container
and
The purpose of this presentation is to go
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1
over the status of the issue of dilution of the oral
2
agreement with Department of Energy and also some
3
aspect of risk assessment in waste package and drip
4
shield performance.
5
I would like to focus in two areas.
The
6
current status of safety demonstration and the status
7
of technical basis. The safety demonstration is based
8
on the best abstracted models based on the current
9
knowledge in the medical manner and on the other end,
10
the technical basis is the evidences and the data base
11
to support the based current models.
12
The
content
includes
basically
13
environmental conditions and the various failure mode
14
of the waste package and drip shield.
15
I will go over one by one as overall
16
perspectives.
17
issues of variations of chemistry in the repository as
18
well as a simulated corrosion test solution. Also, it
19
includes
20
simulated repository solution.
21
different chemistry we've discussed the variation
22
among themselves.
a
The environmental conditions, we have
chemistry
from
--
chemistry
of
the
So we have three
23
The other area is temperature effect.
24
Currently, the repository may go up to 106 degrees C
25
in
the
high
temperature
operation.
The
normal
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1
(unintelligible due to accent, hereinafter, UDTA)
2
corrosion practices needed to be extended to a higher
3
temperature about 100 degrees C.
4
Also, we have issues of coupled processes,
5
thermal,
hydrological,
6
processes.
7
processes involved.
8
9
chemical
and
a
couple
of
In addition to that, we have mechanical
I will go over briefly that.
Also, this assessment involves various
sciences.
People are worried about very aggressive
10
chemical conditions of very low probability.
11
address those aspects as well.
12
The
first
failure
mode
of
I will
the
waste
13
package
materials is uniform corrosion, which means
14
waste package should corrode very uniformly and the
15
probability
16
uniform penetration is very high, like close to one.
17
Next failure mode is localized corrosion
18
which is fast localized penetration such as peeling,
19
crevice
20
probability of occurrence under the current
21
Mountain conditions.
of
occurrence
corrosion.
22
This
of
uniform
failure
corrosion,
mode
has
lower
Yucca
The next failure mode is stress corrosion
23
cracking.
24
uniform corrosion, producing cracks assisted by both
25
stress
as
This is a discrete failure compared with
well
as
chemistry.
It
has
a
lower
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1
probability occurrence.
2
In the drip shields performance, we have
3
all failure modes addressed in the waste package
4
uniform
5
occurrence, a discrete failure of low probability of
6
occurrence.
penetration
7
of
higher
probability
of
I will go over more detail later.
Next
failure
mode
is
materials
aging
8
because we are talking about a time period of 10,000-
9
year period, the microstructure or distribution of a
10
chemistry may be altered which may lead to localized
11
corrosion as addressed previously.
12
This material aging is considered to be a
13
low
probability
14
temperature
15
engineering practice where the material engineer aging
16
is of a concern such as a temperature 1000 degrees C.
17
Next, the failure mode is a mechanical
18
failure which is a discrete failure or a uniform
19
deformation.
20
of drift which is considered to be a low probability
21
of occurrence.
is
occurrence
low
enough
because
compared
still
with
the
normal
One example is rockfall or degradation
22
Juvenile failure, even with the quality
23
assurance and the good design, still, we need to allow
24
certain percentage of waste package to fail initially.
25
Current
data
shows
it
has
a
low
probability
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1
occurrence.
2
The last one is criticality.
3
DOE has taken an approach to assess the criticality
4
using the probability screening.
5
based
6
failure, criticality is considered to be screened out.
7
Therefore, we need to address the criticality issue
8
here with respect to waste package performance.
on
9
very
low
probability
Currently,
In other words,
of
waste
package
I will go over each failure mode and
10
environmental conditions one by one.
The first is
11
environmental conditions. We have one CLST agreement,
12
18 ENFE agreement and four TSPAI agreement with DOE.
13
DOE needs to resolve all those agreements of [UDTA].
14
What we know about these environmental
15
conditions, DOE tested the repository -- simulated
16
repository chemistry at various temperatures up to --
17
above the boiling point and also they established a
18
long-term test at the facility LTTF with various
19
chemistry.
20
Currently, it appears that there is a
21
consistency between the chemistry modeling and test,
22
experimental test chemistry.
23
(Slide change.)
24
DR. AHN:
25
form.
Next slide shows a tabulated
The first column is the ions of our interest
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1
with respect to corrosion.
2
involved.
3
fluoride, carbonate, nitrate and sulfate which are
4
influenced in the corrosion property.
5
However,
Chloride
I
picked
is
up
only
responsible
7
determines the pH of the solution.
Nitrate and
8
sulfate
prevent
9
corrosion.
like
similarly.
localized
corrosion.
more
is
for
chloride,
6
are
Fluoride
We analyzed all ions
inhibitors
to
Carbonate
the
10
The second column is evaporated synthetic
11
J-13 well water as temperature goes up to temperature
12
of
13
leaving the concentrated chemistry on the surface of
14
waste package.
100
degrees
C,
dripping
water
will
evaporate
15
The third column is evaporated synthetic
16
pore water to extend the analysis from the J-13 to
17
pore water and the third column stand out J-13 well
18
water at the higher temperature at 60 degrees and 90
19
degrees
20
chemistries
used
21
facilities.
One is simulated or concentrated water,
22
simulated acidified water and simulated saturated
23
water.
24
25
and
the
As
rest
in
you
of
the
see
the
DOE's
here,
three
columns
long-term
for
are
testing
instance,
the
chloride, there are variations, but at least the test
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1
of conditions pick up the range of chemistry expected
2
from the operated testings.
3
Likewise, fluoride carbonate and nitrate,
4
sulfate
were
5
Nonetheless, there are gaps there, variations there.
6
DOE is giving effort to include other combination of
7
chemistry in their potential static or short-term
8
testing to have a whole range of chemistry.
9
captured
Likewise,
in
at
the
the
actual
center,
testings.
we
do
have
10
confirmatory research, varying the chemistry by taking
11
away or adding up chemistry from the pure solutions.
12
(Slide change.)
13
DR. AHN: This slide shows the temperature
14
profile for two depository operating mode.
15
is low-temperature operating mode.
16
scale of time up to a million years.
17
temperature you could see is only slightly above 80
18
degrees C.
19
On
the
other
hand,
Left one
As you see, the
in
The maximum
the
higher
20
temperature mode, you see the temperature can go up to
21
170 degrees C.
22
corrosion they really do not go temperature of 100
23
degrees C. unless under the pressurized condition. We
24
do not have pressurized conditions.
25
are concerned about [UDTA] corrosion above 100 degrees
In the normal practice of aqueous
Nonetheless, we
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1
C, due to the so-called Deliquesense[UDTA] relative
2
humidity.
3
In the presence of mixed salt, deposited
4
under waste package and drip shield, the effective
5
boiling point may go up because of the low vapor
6
pressures, pressure in the presence of salt as well as
7
capillary effect.
8
9
This is based conditions of temperature
profile.
DOE has chosen currently to go with high
10
temperature mode.
Therefore, we will discuss more
11
extensively the waste package and drip shield behavior
12
at temperature created in 100 degrees C.
13
Environmental conditions data. What kind
14
of testing was done, especially at temperature 100
15
degree C. DOE has limited data in autoclaves and with
16
humid chambers above 100 degrees C. and up to 150
17
degrees C.
18
tests of rock salts are available for Alloy C-4 and
19
titanium 7 up to 200 degrees C over a decade because
20
there are reposited rock salt . It's a more aggressive
21
condition
22
repository.
23
are
24
Nonetheless, they are long term field data are very
25
valuable.
not
Some long-term current data from Germany
with
respect
to
the
Yucca
Mountain
But the method of -- not very desirable,
much
incorporation
of
electro
chemistry.
We are analyzing data.
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1
Lately, the EPRI used some of these data
2
for
their
performance
assessment
in
Phase
6.
3
Likewise, our center effort is to add assessing the
4
high temperature affecting autoclave above 100 degrees
5
C. as well.
6
As I mentioned, we needed in this area,
7
environmental condition is more characterization of
8
above the [UDTA] boiling point, also, in solution
9
chemistry as well as corrosion performance both.
10
There are a number of issues. I cannot go
11
over all details with you today. I have about 40 back
12
up slides.
13
(Laughter.)
14
I will not go over.
I haven't made any
15
copies for you, but if you like to, I can go -- for
16
instance,
17
performance, how mixed salt affected the corrosion,
18
what
19
temperature in turn effect the corrosion behavior;
20
heavy metal impurity effect as raised by State of
21
Nevada, for instance another one is aerosol chemistry.
22
In the presence of drip shield, you can
23
see in any pure water on the surface of waste package
24
because there will be no water drip.
25
have to worry about low pressure corrosion as stress
kind
how
of
coupled
chemical
processes
speciation
affect
at
the
different
Then we don't
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1
corrosion cracking.
2
observed on the pure water and the surface waste
3
package, we still need to consider the low pressure
4
corrosion and the stress corrosion cracking in the
5
presence of the drip shield.
6
hydrogen peroxide condition.
7
condition.
8
may be obtained from a radiolysis.
9
and maybe obtained through radiolysis or from the
10
structure and material in the drip to may dissolved to
11
release ferric ions.
12
waste
13
corrosion or lately the State of Nevada presented low
14
pH conditions from the condensed water, but we need to
15
discuss a lot about the subsequent offering with the
16
geological material or [UDTA] or the waste package.
And the low pH and
This is very aggressive
People are concerned with it.
packaging
17
Nonetheless, if aerosol will be
Hydrogen peroxide
Under this combined condition,
may
Also,
A low pH
the
be
subjected
State
of
to
Nevada
localized
present
a
18
concern about geometric radio integrative result.
19
Nitrate and sulfate may act as inhibitors.
20
if the salt deposit differentially, in other words, at
21
some point [UDTA] floride other point [UDTA] nitrate
22
then at certain point the surface may see a worsening
23
of the conditions.
24
condition as well.
25
However,
We need to take a look at that
Another area is a comparability of waste
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1
package with internal structure, inside waste package.
2
For instance, nitrate is a benefit for a waste package
3
performance.
4
so we need to take a look at that.
5
It's detrimental to internal structure,
We have many uncertainties here.
Also
6
from our a PA perspective, how those uncertainties
7
propagate need to be considered as well.
8
9
If you have questions, I may go to the
back up slides later.
10
The
first
have
eight
mode
CLS7
and
is
uniform
11
corrosion.
12
agreements with DOE in this area.
13
and I leave other topics for future discussion, unless
14
you have questions, then I can go back to the back up
15
slide.
16
We
failure
four
TSPAI
I give you [UDTA]
The data shows the passive layer formed on
17
the uniform corrosion.
Seems to have integrity for a
18
long period of time, based on current knowledge.
19
Currently available data suggests that waste package
20
of life time gradient of 10,000 years.
21
(Slide change.)
22
DR.
AHN:
Next
slide
shows
this
is
23
fraction of penetration of waste package surface as a
24
function of time.
25
Energy.
These data are from Department of
These group of curves are from the data for
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1
various conditions.
One single higher curve from the
2
short-term test like six months and one year.
3
currently planning to use 5-year data which is lower
4
than 6 months or 2-year data.
5
case, within 10,000 years, no container failure is
6
shown here.
DOE is
As you see for any
7
The inference of analog studies suggests
8
long-term passivity and consistent with model for
9
[UDTA].
Lately the center issued very extensive
10
review in the validation of analog studies. We do not
11
have eject analogs with respect to materials and
12
environment.
13
observations made in the analogs with respect to
14
current corrosion theory, then we may predict the
15
future of material as well,
16
more than the corrosion theory, is the main purpose of
17
the study of analogs.
If
we
could
analyze
interpret
the
In other words, validate
18
They covered not just the nickel [UDTA]
19
for instance, not just nickel-based analog but other
20
iron-based, other artifact meteorite, Indian pila or
21
whatever is necessary to validate the modern corrosion
22
theory.
23
similar perspective.
24
25
The theory analyzed [UDTA] as well to see
However, we still need more work.
instance,
MIC,
microbial
induced-corrosion,
For
DOE's
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1
assessment
have
2
elicitation.
3
Mountain repository.
4
wasn't
5
opposed to alive at 60 degree C, but MIC attack means
6
there appears to be no significant MIC.
any
two
sources,
one
from
expert
There will be no MIC in the Yucca
In LTCTF at 60 degrees C. there
significant
MIC
means.
Microbes,
as
7
Under the list of concerns, nitrate, an
8
inhibitor may be consumed quickly by microbe in order
9
to
have
better
rationale,
how
this
affects
10
performance.
11
stuff
12
survived a temperature of 100 degrees C.
13
consider these kind of concerns.
the
[UDTA] Center [UDTA] shows microbes in
from
the
Pena
Blanca
uranium
deposit
mine
We need to
14
Other issues in uniform corrosion included
15
the effect of aggressive chemistry on the uniform code
16
and rate, effect of temperature, especially above the
17
groundwater boiling point.
18
assessed by DOE, EPRI and the foreign country along
19
with the Center.
20
analysis.
21
Also,
Some of these are already
We reviewed all those data and
there
is
a
concern
of
sulfur
22
segregation.
That means sulphur can accumulate at
23
interface within corrosion that exists in the passive
24
filament metal that will lead to falling off of the
25
passive film.
It's a well-observed phenomenon in
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1
industry. This can be mitigated by proper design, DOE
2
is conducting right now an accelerated testing.
3
Also, we have a concern about long-term
4
corrosion potential rise observed in one of the tank
5
DOE ATCTF.
6
artifact due to the release of ions from the tank
7
itself.
There is trying to interpret that is an
We'd like to see their basis for that.
8
(Slide change.)
9
DR. AHN:
Now, next topic subject is
10
localized corrosion.
11
this area.
12
see any localized corrosion up to 95 degrees C. Lower
13
risk significant is considered as Dave mentioned.
14
This statement is somewhat consistent with NRC TPA
15
exercises as well as EPRI analysis.
16
We have four CLST agreements in
Data based includes first LTCTF did not
Other
data
available
in
localized
17
corrosion is higher temperature effects in aggressive
18
solution, tests performed by the Center, aggressive
19
solution of pure sodium chloride at temperature close
20
to 90 degrees C., Alloy C-22 was the subject of
21
localized corrosion.
22
Also, if you have improper micro structure
23
from
welding,
the
material
will
be
subjected
to
24
localized corrosion.
25
up inhibitors such as nitrate and sulphate to pure
Nonetheless, the Center added
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1
sodium chloride and saw the dramatic increase of
2
resistance to the alloy localized corrosion. There is
3
some data of German tests.
4
deducing, nonetheless, under the radiation conditions,
5
we think the oxidized environment formed comparable
6
with our repository.
7
German repository is
At 100 radical hour, they did not see any
8
localized corrosion for C-4.
C-4 is a slightly less
9
corrosion resistant to alloy 22.
And DOE tested
10
localized corrosion on heavy metal, low pH, high
11
temperature conditions and the State of Nevada did
12
under very aggressive conditions.
13
waste
14
appropriation of local corrosion [UDTA] due to the
15
limited supply of the oxidants. There is some evidence
16
of localized corrosion as well, for instance pitting
17
observed
18
concentration which means, demonstrating a validity of
19
localized modern corrosion theory.
package
20
in
panel
ion
Also lately, DOE's
considered
artifact
had
a
the
high
limited
chloride
Still, we need to learn more about in the
21
localized corrosion.
22
temperature above 100 degrees C in a wide range of
23
ground water concentration, including the aggressive
24
solutions.
25
We suggest to fill in there a
Another area of work did include a simple
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1
solution by adding more different species or taking
2
away different species.
3
better
4
localized corrosion and NRC is taking the conservative
5
side, but DOE's critical potential really does not
6
tell a good electrochemical basis and we would like to
7
see that.
basis
for
Also, we'd like to see a
DOE's
critical
8
(Slide change.)
9
DR. AHN:
potential
for
Next failure mode is stress
10
corrosion cracking.
11
this area. Again the data from DOE, the LTCTF results
12
showed no SCC even on the double U-bend specimens.
13
Double
14
aggressive conditions due to the aggressive solution
15
including U-bend.
U-bend
16
We have two CLST agreements in
specimens
means
SCC
tendency
under
You don't see any SCC indications.
As they showed here, the risk of curve,
17
they
assumed
18
significant.
the
SCC
appears
to
be
lower
risk
19
Other data available is DOE and GE showed
20
the SCC under controlled conditions where they applied
21
the potential with a very high straining.
22
natural environment we may not have such conditions,
23
however, the chemical fluctuations at some point may
24
reach such conditions, therefore, we need to see more
25
extensive data to make sure the repository will never
In the
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1
reach such conditions.
2
Center did some conservative evaluations
3
in severe environment and of magnesium chloride in
4
1110 C and so the SCC.
5
approach to mitigate SCC by applying laser peening,
6
the
7
corrosion and cracking.
compressive
stress
DOE has also a different
to
mitigate
the
stress
8
Also, DOE is proposing to design the waste
9
package to mitigate the rockfall stress in the elastic
10
regime. This is a difficult task, so we'd like to see
11
how that task is implemented.
12
cracked measurement to sensitivity, less than one
13
micron so that they can predict the crack behavior for
14
10,000 year properly.
15
DOE also improved the
The State of Nevada have heavy metal, low
16
pH, high temperature condition testing.
Some of DOE
17
analogy produced very well.
18
But again, those tests were done in a very severe
19
environment for the purpose of extrapolating to really
20
positive conditions.
21
available.
22
I guess tests again is valuable because they did test
23
up to 200 C.
It's another concern.
And the German tests also are
Some of them are used by EPRI PA lately.
24
Work needed: we'd like to suggest to fill
25
in data at temperature above 100 degrees C and a wider
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1
range of groundwater concentrations including the
2
aggressive solutions. Other work needed area includes
3
heavy metal impurity effect and the fluoride effects,
4
DOE has a concern about this and pursuing to conduct
5
tests.
6
(Slide change.)
7
DR. AHN:
Next issue is a drip shield
8
performance. Drip shield performance includes all the
9
failure mechanisms of waste package itself, but I put
10
together here.
11
our waste package agreements are relevant here.
12
The
We have four CLST agreements and all
risk
with
14
embrittlement which are not in the waste package
15
performance; and stress corrosion cracking.
16
risk is lower significant as Dave mentioned earlier.
17
However,
18
rockfall.
shield
may
corrosion,
drip
shield
drip
uniform
associated
13
19
includes
factor
mitigate
the
hydride
Overall,
impact
of
What kind of data do we have? We have low
20
corrosion uniform corrosion rates from LTCTF.
21
was a concern of fluoride-enhanced fast corrosion. In
22
the DOE's LTCTF, DOE did not see fluoride-enhanced
23
fast corrosion.
24
such as the effect of nitrate and sulfate.
25
There
Primarily due to the [UDTA] effect,
There appears to be that the fluoride
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1
effects a lower risk, however, the Center did a test
2
under more controlled system and pure sodium chloride
3
solution, added a fluoride and added sulfate, nitrate
4
gradually.
5
corrosion rate with the fluoride additions.
6
need to clarify better why LTCTF did not see the
7
fluoride effect, if fluoride uniform corrosion rate is
8
increased a couple order of magnitude, the drip shield
9
life will be reduced a couple of order of magnitude as
They still saw the [UDTA] of uniform
10
well, like 100,000 years.
11
clarify that.
So we
So it's important to
12
No drip shield localized corrosion was
13
observed in LTCTF, also in German repository up to 200
14
degrees C, under radiation condition. Although lately
15
DOE saw stress corrosion cracking under the slowest
16
hydrogen
17
solution,
18
observation, probably we would like to see how this
19
observation affected the overall risk of association
20
[UDTA] of failure as well as waste package failure.
condition
DOE
at
raised
110
a
degrees
panel
21
(Slide change.)
22
DR. AHN:
C
caution
in
[UDTA]
about
this
Work needed -- we would like to
23
suggest to confirm the lower risk significant with
24
respect
25
embrittlement is unique failure phenomenon in titanium
to
hydride
embrittlement.
Hydride
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1
compared with C-22 because the hydrogen entry from the
2
corrosion will not be fast.
3
hydrogen to form the hydrogen is a very large amount,
4
the risk is considered to be of low significance.
5
However, as I discussed, if fluoride accelerated
6
corrosion rate, then a hydrogen uptake will increase,
7
so this is related concern.
8
rationale for that, including the height.
Also, the amount of
the
We need to see better
9
Also, critical hydrogen concentration to
10
initiate the embrittlement is under debate by now. We
11
have all literature from DOE and EPRI to establish our
12
basis right now. Currently, this is an agreement with
13
Department of Energy.
14
Again,
it
is
difficult
to
obtain
the
15
rockfall stress in the elastic regime, so we'd like to
16
see how DOE implements the proper design to avoid the
17
larger stress applied.
18
(Slide change.)
19
DR. AHN:
This is DOE's risk assessment
20
drip shield, associated with drip shield performance.
21
Here, the dose rate of millirem per year, this is
22
time.
23
shield, enhanced drip shield. All cases show the dose
24
rate is very low after 10,000 years.
As you see here for base case, degraded drip
25
(Slide change.)
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DR. AHN: Our next topic is thermal aging.
2
We have six CLST agreements.
3
driven long range ordering and the precipitations are
4
unlikely under the repository conditions.
5
of
6
localized corrosion and stress corrosion cracking. We
7
do
8
repository condition, mainly due to a low temperature.
solid
not
state
think
9
DOE
base
this
transformation
is
is
We consider thermally
a
likely
trying
to
may
This type
lead
phenomenon
collect
some
to
under
analog
10
observation of the stability of basis from [UDTA].
11
Again, we have specific agreements with DOE suggesting
12
the measurement of factor to time for transformation
13
at high temperature around 800 to 900 degrees C. They
14
measured
15
accelerated conditions, like at 800, 900 degrees C,
16
extrapolated.
17
accurate, the extrapolation consequently would not be
18
accurate,
19
measurement here.
20
the
so
transformation
If
the
we'd
temperature
measurement
like
to
see
here
more
under
are
not
accurate
Other work needed include better initial
21
sample characterizations.
22
extrapolation of the aging in a long-term period and
23
cooling rate effect.
24
mark up testing to see this type of phenomena.
25
Again, they had to factor
DOE is conducting right now the
(Slide change.)
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1
DR. AHN: Mechanical failure included many
2
more [UDTA].
3
agreements and 2 TSPAI agreements.
4
right now as Dave mentioned.
5
on
6
mainly due to the probability to occur.
Even without
7
waste package you expect a low dose.
Then if you
8
multiply the probability, you could expect a lower--.
9
There is a sequence of events associated with drip
10
collapse like drip collapse probability, rockfall
11
probability, rock size distribution and so forth.
12
It's all probabilistic. Nonetheless, we would like to
13
suggest to evaluate drift degradation better, make
14
sure there will not be high risk phenomena there.
15
Other areas we would like to see better rationales:
16
impact of loading from discrete rock blocks, static
17
loads from rockfall, inducing the crib of a waste
18
package
19
Again,
20
incorporate that. The corrosion process, as time goes
21
on, the thickness of container and drip shield will be
22
reduced, therefore, stress will be reduced as well.
current
23
of
it
We have 7 CLST agreements and 5 RDTME
understanding
drip
is
shield.
A current notion based
is
low
area
risk
Seismic
probabilistic,
Another
It is of concern
is
but
significant
ground
DOE
whether
motion.
needs
the
to
drip
24
degradation at some point at the property of water
25
seepage and temperature will change and temperature
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1
may rise. Something like emplacement of backfill with
2
the rocks.
3
analysis of backfill. We then without backfill mainly
4
temperature will rise.
5
much.
6
with drip degradation.
7
valuable interpretation of the risk associated drip
8
degradation.
For instance, this is earlier DOE's
The windows did not change
We like to have a better assessment associated
9
This kind of curve will be
(Slide change.)
10
DR. AHN:
Next topic is juvenile failure.
11
Again, we do not have any agreement with DOE on
12
juvenile failure per se, however, we have agreement in
13
the criticality with DOE which deals with juvenile
14
failure.
15
What
is
the
source
of
the
juvenile
16
failure?
Those include detection limit of flaw size,
17
initial
18
cracking.
Here, [UDTA] means only a period like 10
19
years,
years,
20
materials
in
21
improper
heat
22
thermal output outside the expected range during the
23
welding.
24
Right now DOE considered less than one waste package
25
failure, but we are considering more than that, about
flaw
15
size;
human
{UDTA]
welds,
error,
subsequently.
especially
treatment;
stress
filler
surface
corrosion
Improper
material;
contamination;
All those will lead to juvenile failure.
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1
30 waste packages initially.
2
Work needed in this area is detection
3
limits.
Current technology such as ultrasonics or
4
x-ray has a certain limit of detecting the flaw size.
5
We have better bases for that.
6
Also,
all
data
bases
used
were
from
7
performance of steels, not specified in C-22. We have
8
better rationale why those data are C-22 or titanium
9
drip shield.
10
Last one is -- this is closed welding with
11
remote control. All commercial data base are not from
12
remote control, so they need to consider how this
13
remote
14
juvenile failure rate.
15
reduce the juvenile failure rate or remote control may
16
increase the juvenile failure rate.
17
the [UDTA] for that.
18
NRC's component reevaluation uses about [UDTA] higher
19
juvenile failure rate right now.
control
or
automatic
the
We'd like to see
On a conservative basis, the
(Slide change.)
21
DR. AHN:
CLST
affect
Otherwise, the control may
20
seven
control
Last one is criticality.
agreements.
Criticality
may
We
22
have
be
23
discussed separately in another meeting.
24
I have brought this one here is that criticality is
25
planned to be screened out based on the long-term
The reason
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waste package lifetime.
2
Screening, based on low waste package of
3
probability is the key to the current criticality
4
assessment.
5
Preliminary NRC's confirmative consequence
6
assessment showed similar lower risk with steady-state
7
and transient criticality.
8
9
We'd like to see though a better based for
probability screening.
They have already changed the
10
position a few times.
11
waste package, 100 percent waste package integrity.
12
Later on they change the probability of water infusion
13
into failure container is a loss, assuming waste
14
package
15
justification for all those scenarios.
failures.
So in the beginning its entire
So
we've
16
(Slide change.)
17
DR. AHN:
like
to
see
a
good
In conclusion, DOE assessed the
18
environmental conditions of waste package and drip
19
shield
20
groundwater boiling point.
21
fill in data at temperatures above the groundwater
22
boiling
23
conditions need to be better characterized.
24
25
extensively
point.
The
at
temperature
the
It is suggested that DOE
Especially,
uniform
below
aggressive
corrosion
rates
chemical
of
waste
package are extremely low. Analog evidence and models
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1
provide an insight of long-term passivity.
2
is
3
temperatures and under aggressive chemicals condition.
4
For example, uniform corrosion rate under crevice
5
environments, these are to be characterized.
6
one agreement with DOE in this area.
suggested
7
No
that
DOE
fill
localized
in
data
corrosion
Again, it
at
and
higher
We have
SCC
were
8
observed in DOE's LTCTF at temperatures below the
9
groundwater boiling point.
It is suggested DOE fill
10
in data at higher temperatures and under aggressive
11
chemical conditions.
12
appears to be a lower risk significant.
13
my back up slide, we did a risk assessment using NRC's
14
code assuming a stress corrosion cracking, assuming a
15
localized corrosion and so forth.
16
significant effect there.
The assumed localized corrosion
17
(Slide change.)
18
DR. AHN:
Actually, in
We did not see a
The risk associated with drip
19
shield failure is lower significant.
It is suggested
20
that DOE provide again proper design to mitigate
21
inelastic rockfall effects which may cause the drip
22
shield failure.
23
The current assessment of rockfall effects
24
is suggested to include drift degradation, creep,
25
impact, and corrosion processes.
As Dave mentioned
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earlier, this is an area we need to clarify for them.
2
Although the juvenile failure may be lower
3
risk significant, better data bases are suggested for
4
a detection limit of flaw size, remote control and
5
materials specific performance.
6
The last one is the criticality, is lower
7
risk significant.
8
DOE
9
screening.
obtain
a
Nonetheless, it is suggested that
better
basis
for
the
probability
10
Thank you.
11
VICE CHAIRMAN WYMER: Thank you very much.
12
I had a couple of questions.
13
DR. AHN:
Yes.
14
VICE CHAIRMAN WYMER:
There's a lot of
15
additional work in this area, ranges somewhere between
16
very large and huge and I wondered what sort of
17
screening criteria are you planning to use or would
18
you suggest with respect to the -- which are more --
19
which of these things are more important to carry out
20
and on what time schedule based on a risk-informed way
21
of evaluating?
22
23
DR. AHN:
I didn't catch your
question quite clearly.
24
25
Yes.
VICE CHAIRMAN WYMER: There's a lot to do.
How do you decide what to do first?
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DR. AHN:
They started with researching
2
well water.
3
However,
4
repository, they tested the chemical chemistry of the
5
evaporated solutions which was shown in the beginning.
6
And
7
solution for corrosion testings in all the time to use
8
in LTCTF.
9
[UDTA].
in
Then later on pore water was introduced.
because
the
of
the
meantime,
high
they
temperature
simulated
at
the
evaporated
There is some consistency there with
Nonetheless, there are variations.
Again,
10
those -- with those solutions you do not see localized
11
corrosion in SCC and SCTF up to 90 degrees C.
12
terms of risk, there is no localized corrosion there
13
and no cracks formed there, so risk was assessed based
14
on uniform corrosion rate with those solutions.
And in
15
For instance, in the Center's assessment
16
was based on pure sodium chloride solution to raise
17
the issues concerned on the aggressive conditions. So
18
we did some risk assessment varying the chloride
19
concentration from the J-13 to LTCTF concentration up
20
to the [UDTA] limit.
21
within 10,000 years, but still risk was very low.
22
in addition, DOE is doing testings in a combination of
23
various chemical species.
24
do a long-term testing for all permutations, but based
25
on
current
corrosion
We saw some localized corrosion
So
I don't think anybody can
theory,
they
selected
LTCTF
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chemistry as well as combination of key component in
2
short-term testings.
3
VICE CHAIRMAN WYMER:
I probably haven't
4
phrased my question clearly enough. There's a lot yet
5
to
6
application and some of these questions you'll want
7
the answers to in order to evaluate their license
8
application. Some of the questions can wait while the
9
licensing process is underway.
be
done.
DOE
will
come
in
with
a
license
10
How will you decide what information DOE
11
has to have at the time of their license application
12
and how will you decide what is, which of -- and part
13
of that, how are you to say which of these is most
14
important and therefore should be done before the
15
license application?
16
DR. AHN:
I don't think I can answer your
17
question on the basis of quantity, but I presented to
18
you DOE has evidence of no stress corrosion cracking
19
or localized corrosion from ATCTF.
20
high temperature test results from Germany or Center,
21
so what I would like to present today, the current
22
status, what we know to close the old agreement by LA.
23
The final decision will be made by Licensing Board
24
whether there is sufficient information to the safety
25
case.
I have brought
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All we needed to do is bring about all the
2
DOE's
evidence,
3
Center's evaluation to the Licensing Board.
4
VICE
international
CHAIRMAN
committee
WYMER:
evidence,
Okay,
another
5
question.
I'm sure you remember a while back the
6
consultants from Nevada made a big to do about the
7
effects of mercury and lead.
8
DR. AHN:
9
VICE CHAIRMAN WYMER:
10
11
DR. AHN:
And corrosions.
Yes, high heavy metal impurity
factor.
12
13
Yes, I addressed that.
VICE CHAIRMAN WYMER:
Where does that
stand right now?
14
DR. AHN:
Right now, Ron is here.
As I
15
understand correctly for localized corrosion, the
16
heavy impurity effect was observed under very severe
17
condition.
18
Nevada was to accelerate that.
The aim of the testing of the State of
19
However, in the stress corrosion cracking,
20
as I understand correctly, the State of Nevada [UDTA]
21
produced the early observation.
22
VICE CHAIRMAN WYMER:
I see.
One final
23
question before I turn the rest of the Committee loose
24
on you. With respect to criticality, that probably is
25
a nonstarter for commercial fuel in a repository.
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DR. AHN:
Yes.
2
VICE CHAIRMAN WYMER:
But there will be
3
DOE spent fuel in there, some of which is very high
4
enrichment stuff.
Have you analyzed that?
5
DR. AHN: Yes. Right now they are focused
6
-- Meraj is here, focusing on the -- moderator that
7
water cannot get in, but you're right, actually,
8
there's a concern about graphite, degrees of [UDTA]
9
variant DOE fuel.
10
Meraj will make a comment on that
further.
11
MR. RAHIMI:
Meraj Rahimi, NRC staff. I
12
guess to answer -- provide a short answer. I mean DOE
13
has submitted to us a topical report which outlines an
14
entire
15
potential for criticality.
16
high
17
methodology applies to that waste form.
18
DOE's approach is that probability of water getting
19
into the waste package is low, so you need the water
20
to get into the waste package, corrode the internal
21
component that could [UDTA] controlled system for it
22
to go -- to have the potential for criticality.
23
right now, DOE's approach is approaching from the
24
probability point of view.
methodology
enriched
25
for
analyzing
DOE-owned
looking
at
the
And your question about
SNF,
that's
also
the
Basically,
So
VICE CHAIRMAN WYMER: That's considered to
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be a low probability by DOE also.
2
MR. RAHIMI: That's right. At this point,
3
they said because of the long waste package life, the
4
probability and of course, we are, the staff, is doing
5
independent analysis.
6
consequence side of it.
We're approaching from the
7
VICE CHAIRMAN WYMER:
8
MEMBER LEVENSON:
Thank you.
But doesn't DOE also
9
intend for all of the research reactor fuel which was
10
highly enriched to dilute it before burying it, before
11
sending it to the repository?
12
I think there's a program at Savannah
13
River to dilute that so that the highly enriched
14
research reactor fuel does not go into the repository
15
as such.
16
VICE CHAIRMAN WYMER:
study
group
a
while
Well, I was in a
17
little
18
specifically at this issue and they dilute some of it,
19
that's true, but there are some very high enriched
20
stuff that they're just going to package up and stick
21
in there.
22
John?
23
MEMBER GARRICK:
back
that
looked
How much influence on
24
what you do is the peer-review work that's been going
25
on
with
respect
to
especially
the
waste
package
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1
issues?
2
3
DR. AHN:
I don't know what you mean
"influence".
4
MEMBER GARRICK:
for
example,
5
study,
6
materials not be used in the drip shield.
7
DR. AHN:
8
MEMBER
9
10
has
Well, the peer-review
suggested
that
certain
Yes, I mentioned that.
GARRICK:
Yes.
And
I'm
just
curious, how much of what they have found correlates
with the work that you're doing?
11
DR.
not
AHN:
just
Actually,
DOE's
I
tried
to
put
12
together
13
reviews'
14
International Review Committees.
15
and one example is stress corrosion cracking of drip
16
shield.
comments
including
peer-
NWTRB
comment,
TSPA
and
17
MEMBER GARRICK:
18
DR. AHN:
19
Centers
I put together all
Right.
Which was raised by peer review
group.
20
MEMBER GARRICK:
21
DR. AHN: I mentioned that. I don't think
22
anything new arrived there.
23
comments.
24
25
MEMBER GARRICK:
Right.
I copied lots of those
Given the views of the
peer- review group and this information about the drip
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1
shield, I would -- are questions beginning to be
2
raised about the basic design and the basic need of
3
the drip shield?
4
that billion dollars?
5
6
In other words, do we need to spend
DR. AHN:
Well, again, our mission is not
the cost analysis.
7
MEMBER GARRICK:
I know it isn't, but it
8
is performance.
Your mission is to deal with the
9
issue of performance and our interest is in the
10
effectiveness of these various barriers with respect
11
to safety and based on some of the material that you
12
presented today and some of the material that's in the
13
peer-review report, there's serious questions about
14
the effectiveness of the drip shield.
15
DR. AHN:
Yes, I agree.
16
MEMBER GARRICK: When do we get to a point
17
that there's serious consideration of an alternative?
18
DR. AHN:
19
MEMBER GARRICK:
20
Yes.
Or different type of
design or even an abandonment of the drip shield?
21
DR. AHN:
Right, there are a couple of
22
functions of drip shield that we are considering right
23
now.
It's a rock shield, one component.
24
MEMBER GARRICK:
25
DR. AHN:
Yes.
The other one is water drip --
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1
MEMBER GARRICK:
2
DR. AHN:
then
If the aerosols are really
3
benign,
4
important role because it prevents the water drip not
5
deposit in the salt and waste package, but if aerosol
6
does, drip shield may be do anything. Again, there is
7
a role of rock shielding there.
8
9
10
the
Water.
drip
MS. BLOOMER:
this?
shields
Hi.
This is Tammy Bloomer.
will
play
a
very
Can I take a stab at
I'm the CLST Team Lead
currently.
11
MEMBER GARRICK:
12
MS. BLOOMER:
Yes.
While DOE currently has the
13
drip shield as part of what they're putting forward to
14
us, they have indicated that they are not sure whether
15
the drip shield will be there.
16
evaluate it while they have it there, so that we're up
17
on top of it. They may propose another material which
18
at that point we would take a look at, but -- or they
19
may remove it all together and then we will have them
20
reevaluate what that effect has on they've determined
21
how the waste package reacts.
22
We will continue to
We are under the understanding that they
23
may pull it out.
If they do, that's what we're going
24
to ask them to do and we have, as well, evaluated what
25
the waste package may and may not do without the drip
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1
shield based on the projected length of the drip
2
shield as we have it now.
3
DR. AHN:
There was also in the very
4
beginning another motivation for putting titanium
5
there.
6
MEMBER GARRICK:
7
DR.
AHN:
Yes.
They
chose
entirely
two
8
different materials, C-22 and titanium in case liquid-
9
based alloy [UDTA] work, then titanium will prevent
10
the water intrusion.
11
well.
That's the original intent as
12
MEMBER GARRICK:
Right, right.
13
VICE CHAIRMAN WYMER:
George?
14
CHAIRMAN HORNBERGER:
Yes.
John asked my
15
questions, but just as one quick follow-up, to phrase
16
it a different way, if the drip shield were to go
17
away, are you comfortable with the agreements that you
18
have in place now to provide enough information on
19
effects, potential effects of rockfall and things like
20
that?
21
DR. AHN: Most of them, most of them, yes.
22
MEMBER GARRICK:
23
MEMBER LEVENSON:
Milt?
Yes.
I have a rather
24
basic question and that is in almost all cases, you've
25
identified additional necessary information. How much
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1
of those additional necessary information arise from
2
a risk perspective as opposed to just filling out the
3
scientific information because, for instance, Slides
4
19 and 22 show that the performance is the same
5
whether you have a base case, an enhanced drip shield
6
or a degraded drip shield. If that's really the case,
7
why do we need to collect more data of the drip
8
shield?
9
opposed to risk --
10
11
How much of this is scientific interest as
DR. AHN: Right. In the very beginning -second slide.
12
Here
I
mentioned
the
objectives,
the
13
status of safety demonstration, status of technical
14
basis. Safety demonstration was obtained based on the
15
best models with the current understanding of science.
16
That does not mean we do not have uncertainties.
17
Therefore, we need to discuss basis. I don't think --
18
you see, safety demonstration shows those figures.
19
Still, we have good technical basis for that because
20
those demonstrations were made on the best judgment
21
with the current knowledge.
22
How much basis do we need?
McCartin
23
Tim
24
discussed that among ourselves several times.
25
may
address
DR. ESH:
that
I don't now.
issue.
We
Well, this is Dave Esh.
have
I have
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1
a perspective on that.
It's a good comment.
I mean
2
your curves are showing that if you degree or enhance
3
that barrier it doesn't influence the system behavior
4
that much, but you have to be careful because that's
5
purely using the model that you developed and most of
6
these uncertainties that they're talking about, you'd
7
first have to evaluate whether that degradation or
8
enhancement captured those uncertainties that Tae has
9
talked about would be the first thing and I would say
10
for the most part it probably didn't because if -- I
11
don't know if this is true or not, but if the drip
12
shield is preventing significant rockfall or drip
13
collapse damage to the packages, that sequence of
14
events isn't built into the model. So if you take out
15
the drip shield completely, and you never change your
16
rockfall model, you're not going to see an effect from
17
that process.
18
The same thing would apply say if the drip
19
shield was preventing aggressive chemical conditions
20
that would result in localized corrosion of stress
21
corrosion cracking much greater than considered now at
22
early times.
23
model so that when you take out that barrier or
24
degrade it, you're not going to see the effect in your
25
model.
If those things aren't built into your
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1
So your comment is a good one. I think to
2
fully answer it, they would need to do some more work,
3
not necessarily experimental work related to the drip
4
shield,
5
competent.
6
but
more
analysis,
MEMBER LEVENSON:
PA
type
work
to
be
If I can summarize your
7
answer, it's that you're not using risk insights to
8
decide what additional information to get?
9
DR. ESH:
Well, I think we do, but you
10
have to be cautious.
Yes, but that's an example of
11
where you have to be cautious.
12
CHAIRMAN HORNBERGER:
But I think you
13
answered a different question. I think what -- Milt's
14
question is why acquire more information on the drip
15
shield itself, not on the waste package, not on an
16
analysis of what happens if you take the drip shield
17
out, but why require more information on corrosion of
18
the drip shield if, in fact, it doesn't matter?
19
DR. ESH:
But I think that question of
20
whether it matters or not is influenced by the other
21
things that you've put in the model.
22
curves that are close to each other, the degraded,
23
enhanced
24
different, they may have a bigger spread between them,
25
if you've added other things into the model that that
and
the
base
case,
they
So those three
may
be
much
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1
barrier is influencing.
2
DR. AHN:
Before Tim comments, let me add
3
one more thing.
4
incorporated uncertainties here quantitatively, if we
5
know where; for instance, distribution of uniform
6
corrosion rate, distribution of critical potential.
7
We factored uncertainties here.
8
means supporting those observations, how much. He may
9
address that issue.
10
In this safety there was [UDTA].
MR. McCARTIN:
We
What technical basis
Tim McCartin, NRC staff.
11
I think Dave's correct in what he's saying.
We have
12
a
do
13
calculations and you see something that lines up and
14
gee, there's no effect here and the initial reaction
15
is you don't need to do anything more.
16
constantly looking at the risk impact of these things
17
and making sure the code results are truly depicting
18
a good representation of risk. That's one part of it.
19
The other part of it though and this gets
20
to NRC's review of what DOE is doing and the rule
21
looks at the capabilities of barriers and if the
22
Department is coming and they have a drip shield that
23
provides a capability for let's say no water will get
24
on the waste package for say 5,000 years, that's a
25
significant capability.
very
complex
code
and
sometimes
you
the
We are
We'll look at the -- what
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1
they've
claimed
2
information
3
ultimately, we have to decide whether what they're
4
saying
5
significant or not, it may have a limited effect on
6
dose with a waste package that lasts a very long time.
7
But I would argue from a multiple barrier standpoint,
8
if the drip shield can keep water off the waste
9
package for 5,000 years, that's a capability and if
10
they're going to take credit for that, it needs to be
11
supported.
12
we can.
13
strictly at dose and that's important, strictly at
14
dose, may not be as risk-informed, but I think you do
15
need to look at what is the capability of each of the
16
barriers and in that sense the drip shield does
17
provide something that does need to be supported.
is
to
and
whether
support
supported.
that
Now
there's
sufficient
claim.
Because
whether
that's
risk
So yes, we try to be as risk informed as
There are certain things that if you look
18
MEMBER GARRICK: But the capability should
19
be looked at in the context of the dose to the
20
critical group.
21
That should be the starting point --
MR. McCARTIN:
Yes and no because I think
22
the dose calculation can be very misleading sometimes
23
in that regard and I would just point to that there
24
have been claims that it's not a geologic repository.
25
It's completely engineered and I think there are
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1
aspects that dose calculation, it's very easy to jump
2
to the dose number. Sometimes it isn't necessarily as
3
informative as other things and I'll point to there
4
are certain nuclides that never get out.
5
see a dose value from those nuclides.
You never
6
One might argue, well, there's no risk
7
contribution. Well, if you look at it, well, gee, the
8
geology is causing delays later than a million years,
9
potentially. And it's hard to get to that and I guess
10
Dr. Garrick, you might say well, that is part of the
11
risk and somehow you need to pull that out and I would
12
agree, but it gets very difficult if you just look at
13
the dose and I think the multiple barrier requirement
14
is --
15
CHAIRMAN HORNBERGER: But again, not to --
16
to go your example, the example you just used, Tim,
17
given
18
retardation
19
million years, would you turn around and still ask the
20
Department of Energy to provide more information on
21
the performance of zeolites or the saturated zone
22
because we just want to make sure that that barrier
23
really is contributing in the way you think.
24
way of asking for more information, not evaluating the
25
barrier.
this
calculation
of
nuclides
that
that
you
never
describe
appear
for
of
a
It's a
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1
MR. McCARTIN:
is
if
the
has
question
3
retardation factors for americium and plutonium --
5
be
But the
2
4
would
Well, correct.
Department
CHAIRMAN HORNBERGER:
say
They're not the
ones.
6
MR. McCARTIN:
They would need to be
7
supported, but so I think we would ask for the support
8
for what they're claiming.
9
CHAIRMAN HORNBERGER: But your example was
10
for radionuclides that never appear.
11
MR. McCARTIN:
12
CHAIRMAN HORNBERGER:
13
Right, well, those were -Would you ask for
more information on those?
14
MR. McCARTIN:
We wouldn't ask for more.
15
We would ask for the information to support what
16
they're claiming.
17
The other problem with the dose thing, the
18
drip shield is a prime example. If it keeps water off
19
the waste package and if that was the only thing, if
20
it's redundant with the waste package, one might argue
21
it has no risk contribution and when you do the dose
22
calculation, it's very difficult to show that. That's
23
the part, at least I like in the rule that you have to
24
talk to the capability of each of the barriers.
25
somehow
that
capability
should
be
point
to
And
some
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1
ability to potentially affect risk.
2
MEMBER GARRICK:
Yes, but again, what
3
we've tried to stress is that the capability of the
4
barriers is not in an abstract concept.
5
capability with respect to something.
6
MR. McCARTIN:
7
MEMBER GARRICK:
8
It's the
Yes.
We need to keep that in
focus.
9
MEMBER LEVENSON:
Let me expand, Tim, a
10
little bit maybe my question because I understand what
11
you're saying and generically I agree, but if I look
12
at this and every single thing in here has a long list
13
of more additional information, it seems to me the
14
second question to ask is how many of those items of
15
information are important to assess that particular
16
issue?
17
corrosion or is it just to fill out the scientific
18
background?
19
doesn't exist on anything else we do routinely.
20
is a pretty complete package.
21
Is
that
really
necessary
to
assess
the
An awful lot of information here that
MR. McCARTIN:
This
It's a shopping list.
Well, we certainly would
22
like to think that all the agreements are tied to
23
something that has a contribution to performance. And
24
something that's necessary.
25
Having said that, there's no question that
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1
this is a continual process of reevaluating whether
2
some of the information is still necessary and it does
3
evolve,
4
requested, there was a sense that they had an effect.
5
Could we be wrong in some areas?
6
that's --
7
but
certainly
when
MEMBER LEVENSON:
these
things
were
Absolutely.
And
Well, you have many,
8
many more risk insights, both from your own work and
9
DOE work and I think the question of when you're
10
talking about Ray poses a question, there's no way all
11
of this information is going to be accumulated.
12
And so to set priorities, I don't know how
13
you do it other than risk insights, not necessarily
14
just
15
insights.
16
insights into this.
the
computer
TPA
or
TSPA,
but
other
risk
It seems to me you have to introduce risk
17
DR. AHN: Yes. Let me add one thing. Tim
18
mentioned multiple barrier requirement and in case of
19
other concern we may consider those lists.
20
As
I
mentioned
to
you,
the
safety
21
demonstration is based on the current observation.
I
22
stressed for each subject what evidence we had to
23
demonstrate the case, but there are more technical
24
bases, how much do we need should be determined by the
25
Licensing Board during the licensing period.
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1
What
we
are
trying
to
do
is
to
put
2
together all those bases, evidences to support the
3
current safety demonstrations.
4
5
VICE CHAIRMAN WYMER: Andy, what would you
like to ask?
6
MR. CAMPBELL: So is it the opinion of the
7
staff that all the information requested for and all
8
the agreements is necessary prior to licensing or is
9
there
an
attempt
to
reevaluate
the
information
10
requests in some of the agreements in light of your
11
risk analyses?
12
DR. AHN:
We do.
We interact with DOE
13
more like weekly to pursue the closure of the oral
14
agreement,
going
15
agreement.
We
16
agreements by considering what are important factors
17
of risk analysis.
into
are
detailed
seeking
a
aspect
way
to
of
oral
close
all
18
MR. LESLIE: This is Brett Leslie from the
19
NRC staff and I would kind of like to address two
20
things that were actually in Andy's question.
21
two-fold, which is performance confirmation or you
22
know, is there information in the agreements that we
23
expect to come after an initial license application?
24
This is going to be a point of discussion
25
at the upcoming technical exchange for the Fiscal Year
It's
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1
2003 agreements. I think we've gone through a thought
2
exercise inside NRC and at the Center, looking at the
3
their agreements and saying yes, look at the scope of
4
what these things are saying, long term testing.
5
we expect them to turn off the switches and shut down
6
their experiments at the time of license application?
7
That wasn't our intent.
8
requested
9
sufficient information at the time of initial license
10
application on the particular area to make a decision.
11
in
those
So
I
But regardless of what is
agreements,
think
Do
all
the
there
must
information
be
we've
12
requested, we believe is needed prior to license
13
application in the agreements.
14
information
15
confirmation testing.
because
we
Maybe not all the
anticipate
performance
16
The second one was really -- is the staff
17
using risk information to tell DOE what they don't
18
need to do?
19
management is constantly telling DOE to use risk
20
information, to make a case and say yes, we don't need
21
to supply this information.
22
quite some time for the first analysis from DOE with
23
that approach.
24
has to come up and say here's the information or
25
here's the reason why we don't need to do it.
Okay.
That's -- we -- management, NRC
We've been waiting for
We're ready to talk about it, but DOE
It's
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1
not our purview to say well, just trust us and you
2
don't need to do it.
3
information and part of using, doing the risk insights
4
analysis and doing some of these off-line calculations
5
is so that when DOE comes in and say okay, for this
6
agreement
7
calculations for why this information isn't really
8
needed.
9
no, have you considered this uncertainty when you've
10
here's
some
additional
sensitivity
or
We're in the position to say okay, yes, or
done your sensitivity analysis.
11
12
So part of that using the risk
VICE CHAIRMAN WYMER:
Thank you.
That
gets at my question very squarely.
13
MEMBER LEVENSON:
But Brett, I have a
14
little problem with that because generally the things
15
that are in the agreements are because NRC asked for
16
it and DOE submitted and agreed to submit it, to
17
provide it.
18
subsequent
19
really wasn't required in the first place, I think you
20
have an obligation to go back and say we really
21
shouldn't have asked for that.
Now if the person who asked for it by
risk
22
insights
MS. BLOOMER:
and
analysis
decides
it
In fact, we have done that
23
on occasion.
We take a look at -- as Tae mentioned,
24
we take a look at all of the agreements and we discus
25
them with DOE at regular intervals in the CLST team.
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We have come to conclusions about some agreements that
2
we feel are no longer necessary and therefore, we said
3
this is now under a status of closed.
4
ahead and closed agreements, based on the fact that
5
either DOE has provided us information or said that
6
you know, this information probably isn't needed and
7
we've agreed because we've done more testing that said
8
you know, this information isn't needed.
And we've gone
9
If you look at the fluorine that people
10
are talking about and how all of a sudden that that's
11
an issue with the drip shield, if nobody asked about
12
that question to begin with, everybody would assume
13
the drip shield was going to last for the amount of
14
time that DOE said it was going to last and that would
15
have been the end of it.
16
We want technical basis to justify what
17
they say.
These issues that we've put in front of
18
them have all been risk significant in the fact that
19
we asked them the questions and we didn't just ask
20
irrelevant questions. We've done testing. We've read
21
about testing. We've found results that indicate this
22
may not be the whole truth.
23
to help us see the whole truth and from that, these
24
agreements have fallen out.
25
data that says we don't need that agreement any more
Give us some background
When we find some other
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1
or we don't need all that data for that agreement any
2
more,
3
understanding and we have done that as recently as
4
today.
we
discuss
5
6
DOE
and
VICE CHAIRMAN WYMER:
we
come
Thank you.
to
some
That's
very clear.
7
8
with
Are there other questions or comments?
Mike?
9
MR. LEE:
Yes, hi.
I just want to take
10
exception with a statement you made regarding the
11
Licensing Board and none of us here, I think, can
12
certainly speak to what the Licensing Board may or may
13
not do, but in the first instance, DOE is obliged to
14
demonstrate compliance with NRC's regulations and in
15
doing so provide sufficient technical basis for that
16
demonstration.
17
The staff and any potential licensing
18
review would use its own independent judgment and
19
render an appraisal or assessment as to whether or not
20
there's
21
uncertainties and state of knowledge to judge whether
22
or not the regulations have been complied with.
sufficient
23
information
there,
given
The Licensing Board will take all of that
24
information
and
then
render
its
own
independent
25
decision, but I don't think they're going to be the
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1
arbiter as to whether or not DOE needs to provide more
2
information or that there are technical cases --
3
4
DR. AHN:
No, I didn't mean that.
It's
just where there's insufficient information.
5
MR. LEE: The first line of defense in all
6
of this is the staff and they'll prepare a safety
7
evaluation report which will evaluate DOE's compliance
8
demonstrations and that, in turn will be use --
9
DR. AHN: Yes. Before that time, as Terry
10
mentioned, we are going with DOE weekly to close most
11
agreements.
12
MR. LEE:
13
VICE CHAIRMAN WYMER:
14
I understand that.
questions or comments?
15
MR. LEE:
16
VICE CHAIRMAN WYMER:
17
MR. LEE:
18
VICE CHAIRMAN WYMER:
19
You might ask San Antonio.
Might ask what?
San Antonio.
Hello, San Antonio,
do you have any questions or comments?
20
21
Are there other
UNIDENTIFIED SPEAKER:
No, we don't have
any questions.
22
VICE CHAIRMAN WYMER:
Okay, thank you.
I
23
know you have prepared an excellent and very detailed
24
comprehensive set of back up slides.
25
DR. AHN:
Thank you very much.
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1
(Laughter.)
2
VICE CHAIRMAN WYMER:
3
have a set of, if I may.
4
or
5
discussion.
comments,
6
thank
Which I'd like to
If there's no more questions
you
for
a
very
CHAIRMAN HORNBERGER:
7
scheduled
to
8
definitely have it early.
9
have
lunch
from
stimulating
Okay, so we are
1
to
2.
We
can
Are there things that we need to discuss
10
before we break for lunch?
11
discuss.
Or that you want to
12
I think we will not need the recorder
13
after we close for lunch, we won't need the recorder
14
any more.
15
16
Any follow-up discussion you want to have
on what we just heard?
17
VICE CHAIRMAN WYMER:
I don't think so.
18
I think we do have to talk about writing a letter on
19
this issue of waste package performance, but that's
20
another, sort of another time.
21
CHAIRMAN HORNBERGER: Okay. Okay, nothing
22
-- anything else that we need to discuss? Okay, we're
23
going to break until 2 o'clock.
24
25
Adjourned.
(Whereupon, at 12:25 p.m., the meeting was
concluded.)
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